Main Research Findings

1) Administration of GHRP-6 was shown to prevent doxorubicin-induced myocardial damages by activating various prosurvival mechanisms.

2) Treatment with GHRP-6 was found to exhibit pro-autophagic effects in skeletal muscle under both normal conditions and with doxorubicin-induced injury.

 

Selected Data

1) This study conducted by the research team of Berlanga-Acosta et al investigated the cardioprotective potential of the hexapeptide GHRP-6 in a rat model of doxorubicin-induced dilated cardiomyopathy (DCM) and heart failure (HF). Male Wistar rats, weighing 200–250 g and aged 9–10 weeks were housed in groups of three under controlled environmental conditions at the Center for Genetic Engineering and Biotechnology (CIGB), with free access to food and water. All procedures were reviewed and approved by the Institutional Animal Care and Welfare Committee of CIGB. Blood sampling was performed under ether anesthesia, and animals were euthanized by an overdose of 250 mg/kg sodium pentobarbital [1].

The pathological model of DCM/HF was induced through repeated intraperitoneal injections of doxorubicin hydrochloride (Dox), a widely used chemotherapeutic drug known for its cardiotoxic effects. Dox was administered at 2 mg/kg twice weekly on Mondays and Fridays for 52 days. The cumulative dosing regimen was expected to generate progressive left ventricular dysfunction, structural remodeling, and eventually HF. For therapeutic evaluation, GHRP-6, a synthetic hexapeptide with known cardioprotective and cytoprotective properties, was used. GHRP-6 was diluted freshly in sterile saline to 400 μg/mL, and administered intraperitoneally at 400 μg/kg twice daily during the experimental period. Solutions were prepared fresh, stored at 4°C, and protected from light to maintain stability.

The central hypothesis was that GHRP-6, when administered concomitantly with Dox, could attenuate or prevent the structural and functional myocardial damages associated with Dox treatment, thereby reducing the onset and severity of DCM/HF. Thirty-six rats were used and divided into three experimental groups of twelve animals each. The first group consisted of healthy, untreated sentinel rats, which were included to provide echocardiographic and biochemical reference values at the end of the study. This control was important because the rats were still in their growth phase during the 52-day period, and age-related changes in cardiac physiology had to be accounted for. The second group received GHRP-6 concomitantly with Dox according to the described regimen. The third group received normal saline concomitantly with Dox and served as the disease control. Before initiating Dox treatment, all animals underwent baseline echocardiographic evaluations to establish pre-treatment cardiac function. Serial echocardiography was subsequently performed on days 14, 24, 37, and 52 to track disease progression and potential protective effects of GHRP-6. By day 52, cumulative Dox exposure reached 30 mg/kg, at which point significant LV dilation and functional failure are known to occur, consistent with prior models [1].

Echocardiographic assessments were performed with sedation using 50 mg/kg of intraperitoneal ketamine and 5 mg/kg of xylazine, ensuring stable positioning. Transthoracic echocardiography was conducted using a Sonos 5500 system with an 11–15 MHz linear transducer. The main structural parameters assessed included LV diastolic diameter, LV systolic diameter, interventricular septal thickness during systole, and LV posterior wall thickness during systole. The left ventricular ejection fraction was considered the primary functional marker of cardiac performance, as established in previous studies [1].

At the end of the 52-day protocol, animals were euthanized unless they had already developed irreversible terminal HF, in which case early euthanasia was performed for humane reasons and proper tissue collection. Autopsies were carried out following standardized procedures, with gross pathological changes documented. Heart, liver, and lung weights were measured to calculate relative organ weight indices, which serve as indirect indicators of organ congestion and hypertrophy. The hearts were cut into four sagittal slices for systematic evaluation. Tissues were fixed in 10% buffered formalin, embedded in paraffin, and sectioned at 2–3 μm thickness for hematoxylin and eosin staining. Semi-quantitative histopathological assessments were performed for cardiac tissue as well as for potential congestion in the liver, kidneys, and bronchial mucosa. Independent blinded pathologists evaluated the samples, and representative photomicrographs were obtained using light microscopy.

For ultrastructural analysis, myocardial tissue samples were prepared for transmission electron microscopy. Samples were fixed with glutaraldehyde, post-fixed with osmium tetroxide, dehydrated in ethanol, embedded, and cut into ultrathin sections. Sections were stained with uranyl acetate and lead citrate, mounted on copper-nickel grids, and examined under an electron microscope. Twenty photomicrographs were analyzed per sample to assess pathological changes in myofibrils, mitochondria, and intercellular junctions, with evaluations performed blindly by a specialist [1].

Blood samples were collected from the retro-orbital plexus at designated time points under anesthesia. Serum was separated by centrifugation and stored at –80°C for biochemical analysis. Markers of oxidative stress and antioxidant enzyme activity were quantified, including total hydroperoxides (THP), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase. THP and MDA levels were measured using commercial kits following manufacturer instructions, while SOD activity was determined via inhibition of pyrogallol autoxidation. Catalase activity was assessed by monitoring hydrogen peroxide decomposition. Additionally, alanine aminotransferase (ALAT) levels were quantified using an automatic analyzer to evaluate potential hepatotoxicity.

To further assess molecular mechanisms, gene expression analysis was performed on LV tissue samples from five rats each in the saline and GHRP-6 groups. The focus was on the balance between pro-survival and pro-apoptotic gene expression. Total RNA was extracted with Tri-Reagent, purified, and treated with DNaseI to remove genomic DNA contamination. Reverse transcription PCR (RT-PCR) was performed using a commercial kit, with β-actin as the housekeeping gene for normalization. Amplified products were separated by agarose gel electrophoresis, and band intensity was quantified with Kodak ID software to assess relative gene expression ratios [1].

2) The research team of Yu et al designed this study to evaluate the effects of GHRP-6, a selective growth hormone secretagogue receptor (GHSR) antagonist, on skeletal muscle under conditions of both normal physiology and doxorubicin (DOX)-induced toxicity. The experimental model used was the C57BL/6 male mouse, aged between 8 and 12 weeks. These animals were housed under a controlled 12:12-hour light–dark cycle and provided unrestricted access to food and water throughout the experimental timeline [2].

The experimental design incorporated several treatment groups to test the role of GHRP-6 alone and in combination with other pharmacological antagonists. Mice were randomized into seven groups: a saline control group (CON), a saline control treated with GHRP-6 (CON + GHRP-6), a doxorubicin-only group (DOX), a doxorubicin group treated with GHRP-6 (DOX + GHRP-6), a doxorubicin group treated with GHRP-6 and the GHSR antagonist YIL781 (DOX + GHRP-6 + YIL781), a doxorubicin group treated with GHRP-6 and the CCR5 antagonist TAK-779 (DOX + GHRP-6 + TAK-779), and finally a doxorubicin group treated with GHRP-6 alongside the CXCR4 antagonist AMD3100 (DOX + GHRP-6 + AMD3100). Group sizes ranged from four to seven animals.

For groups receiving doxorubicin, the drug was administered intraperitoneally at a dose of 15 mg/kg body weight. This was performed in all DOX-containing groups, while control groups received an equivalent volume of saline. Twelve hours after doxorubicin administration, animals assigned to receive GHRP-6 were treated with the peptide at a dosage of 3.75 mg/kg body weight, given intraperitoneally every 12 hours for four consecutive days. This dosing regimen was selected based on previously published studies that established its pharmacological relevance. In groups where additional receptor antagonists were tested, 10 mg/kg YIL781, 10 mg/kg TAK-779, or 10 mg/kg AMD3100 were injected prior to each GHRP-6 administration. At the end of the four-day treatment period, all mice were euthanized with an overdose of ketamine and xylazine. The gastrocnemius muscles were then excised, washed in cold phosphate-buffered saline, snap-frozen in liquid nitrogen-cooled isopentane, and stored at −80 °C until analysis [2].

Histological examination of muscle morphology was performed on transverse cryostat sections 20 µm thick, prepared at −20 °C. These sections were air-dried, fixed in 10% formalin, and stained using Mayer’s hematoxylin and eosin, followed by mounting and imaging of each section. Quantitative analyses included the number of muscle fibers, the proportion of fibers exhibiting centralized nuclei as a marker of regeneration, and fiber size, which was assessed by Ferret diameter measurements across multiple non-overlapping fields. In total, more than 500 muscle fibers were evaluated per sample using ImageJ software to ensure sufficient statistical assessment [2].

For biochemical analysis, muscle proteins were extracted following a previously established protocol. Tissue homogenization was conducted on ice using a lysis buffer containing NaCl, MgCl₂, HEPES, DTT, glycerol, and Triton X-100. Following centrifugation at low speed to pellet nuclei and debris, supernatants were further centrifuged to remove residual nuclear material. The resulting cytoplasmic fraction was supplemented with protease inhibitors, stored at −80 °C, and later used in assays for apoptotic cell death and Western blotting.

Apoptosis was quantified using a cell death detection ELISA kit, which measures DNA fragmentation. Wells of microplates were precoated with an anti-histone antibody and incubated with muscle extracts. Samples were then exposed to a secondary peroxidase-conjugated anti-DNA antibody. Colorimetric detection of peroxidase activity was performed using the ABTS substrate, and absorbance was read at 405 nm. Results were normalized to the protein concentration of each sample, yielding an apoptotic DNA fragmentation index.

Western immunoblotting was conducted to examine protein expression related to key signaling pathways and cellular stress responses. Proteins assessed included components of the Erk1/2 and Akt pathways, markers of oxidative stress, insulin-like growth factor-1 (IGF-1), apoptotic regulators (Bax and Bcl-2), and autophagy-associated proteins. Following denaturation and electrophoresis on polyacrylamide gels, proteins were transferred to nitrocellulose or PVDF membranes, depending on the target protein. Membranes were blocked, incubated overnight with specific primary antibodies, and probed with HRP-conjugated secondary antibodies. Detection was achieved through chemiluminescence, and signals were captured with a BioRad Chemidoc MP system. Band intensities were quantified using ImageJ, normalized to GAPDH as a loading control, and expressed as percentage changes relative to the saline control group [2].

In summary, this study examined the effects of GHRP-6 on skeletal muscle integrity under conditions of doxorubicin-induced stress. Through the integration of histological, biochemical, and molecular approaches, the protocol allowed for the detailed assessment of muscle fiber structure, apoptosis, and alterations in signaling pathways related to survival, stress, and autophagy. By including pharmacological antagonists targeting GHSR, CCR5, and CXCR4, the researchers also aimed to clarify the specific receptor-mediated mechanisms through which GHRP-6 influences muscle pathology and recovery [2].

 

Discussion

1) The study performed by Berlange-Acosta et al investigated the protective role of GHRP-6 in a rat model of Dox-induced cardiotoxicity and systemic organ damage. Over the course of three weeks of Dox administration, the animals developed a cachectic process accompanied by progressive clinical deterioration. Behavioral changes included social withdrawal, prostration, bristly hair, and hunched postures, all characteristic of severe systemic decline. Both saline- and GHRP-6-treated groups exhibited significant body weight loss compared to healthy sentinel rats, indicating that GHRP-6 did not prevent the cachectic weight loss induced by Dox. However, survival outcomes were dramatically different: while only 42% of saline-treated animals survived to the end of the study, 84% of those receiving GHRP-6 remained alive, demonstrating a marked survival benefit associated with peptide intervention. Additionally, autopsy findings revealed that GHRP-6 significantly reduced pathological increases in relative heart and lung weights, aligning these measures with values observed in healthy animals [1].

Cardiac imaging through echocardiography revealed that GHRP-6 provided strong protection against Dox-induced ventricular remodeling and functional decline. At baseline, all rats had normal heart morphology and function, with an average left ventricular ejection fraction of approximately 93%. In saline-treated rats, early myocardial damage appeared by day 24, marked by a significant increase in left ventricular systolic diameter. By day 37, the left ventricular diastolic diameter was also enlarged, accompanied by progressive thinning of the interventricular septum and posterior wall. These changes culminated in a marked 30% decline in left ventricle ejection fraction by day 52, confirming substantial Dox-induced systolic dysfunction. In sharp contrast, rats receiving GHRP-6 showed preserved ventricular diameters and wall thicknesses, with left ventricle ejection fraction values remaining within the normal range throughout the study. The structural and functional parameters in the GHRP-6 group were statistically indistinguishable from those in healthy sentinel rats, suggesting that the peptide prevented the adverse cardiac remodeling and systolic failure typically induced by cumulative Dox exposure.

Figure 1: Changes in A) systolic diameter, B) diastolic diameter, C) septal thickness in systole, D) posterior wall thickness in systole, and E) left ventricle ejection fraction.

Histological analysis supported these imaging findings, showing that GHRP-6 exerted a protective effect at the microscopic level. In saline-treated animals, Dox caused characteristic myocardial abnormalities, including myofibril thinning, undulation, fractures, and patchy loss of staining affinity. These pathological features reflected severe disruption of ventricular myofibrillar architecture. By contrast, rats treated with GHRP-6 exhibited a pronounced “sparing effect,” with myocardial tissue showing only minimal damage. Quantitative morphometric analysis confirmed this difference, reporting 91% of ventricular myofibrils were damaged in the saline group compared to just 42% in the GHRP-6 group. Moreover, myocardial histology in GHRP-6-treated animals was nearly indistinguishable from that of healthy sentinels, reinforcing the cardioprotective action of the peptide [1].

Beyond the heart, GHRP-6 intervention also shielded extracardiac organs from Dox-related toxicity. Histological examination revealed significant congestive heart failure-associated pathologies in saline-treated rats, including passive liver congestion, pulmonary edema with alveolar septal thickening and hypercellularity, and venous congestion. These lesions were largely absent or attenuated in GHRP-6-treated animals. Consistent with histological findings, circulating markers of hepatic injury such as ALAT were significantly elevated in the saline group but remained lower in GHRP-6 animals. In the liver, perivascular fibrotic induration and focal necrosis were prominent in saline-treated rats but absent in those receiving GHRP-6. Similarly, intestinal toxicity manifested as transmural necrosis in the jejunum and ileum in the saline group, while these injuries were consistently prevented by peptide treatment. Renal tissue from saline-treated animals displayed severe tubular epithelial damage, including cytoplasmic ballooning and nuclear pyknosis, whereas GHRP-6 preserved normal tubular architecture. Bronchial epithelium in saline-treated rats showed widespread coagulative necrosis, which was substantially reduced with GHRP-6 intervention. These findings collectively demonstrated that GHRP-6 conferred broad systemic protection against Dox-induced organ injury [1].

The study further explored mechanisms underlying GHRP-6’s protective effects, focusing on oxidative stress and apoptotic regulation. Dox treatment in saline animals significantly elevated oxidative stress markers such as THP and MDA, reflecting increased lipid peroxidation and redox imbalance. These elevations were markedly attenuated in the GHRP-6 group at both intermediate and final time points collected at day 35 and day 52, respectively. Enzymatic antioxidant defenses also followed distinct trajectories between groups. Catalase activity initially increased in both groups during early Dox exposure but later became suppressed as cumulative toxicity mounted, with a more profound decline in saline-treated rats. GHRP-6 attenuated this inhibition, maintaining higher catalase activity through the late stages of treatment. SOD activity, which declined progressively in saline-treated animals, was preserved in those receiving GHRP-6. Together, these findings indicated that GHRP-6 helped maintain redox homeostasis and reduce oxidative cytotoxicity during Dox treatment.

At the molecular level, GHRP-6 shifted the balance of pro- and anti-apoptotic gene expression in favor of cell survival. Specifically, the peptide upregulated Bcl-2 expression while suppressing Bax, two central regulators of the intrinsic apoptotic pathway. The resulting increase in the Bcl-2/Bax ratio was significantly higher in GHRP-6 animals compared to both saline-treated and healthy sentinel rats. This suggests that GHRP-6 not only counteracted Dox-induced pro-apoptotic signaling but also enhanced protective survival pathways in cardiomyocytes [1].

Finally, ultrastructural analysis using electron microscopy revealed that GHRP-6 preserved cardiomyocyte integrity at the organelle level. In saline-treated rats, Dox exposure caused sarcolemmal vacuolization, myofibrillar fragmentation, and extensive mitochondrial injury, including swelling, cristae disruption, and membrane dilation. By contrast, GHRP-6-treated cardiomyocytes maintained intact sarcolemmal and mitochondrial structures, with minimal evidence of injury. This preservation of subcellular architecture provided direct evidence of the peptide’s protective role against Dox-induced cellular degeneration.

In summary, GHRP-6 demonstrated a multifaceted protective profile in a rat model of Dox-induced toxicity. While it did not prevent cachexia or weight loss, it significantly improved survival, preserved ventricular structure and function, and reduced systemic organ damage. Mechanistically, its benefits were mediated through attenuation of oxidative stress, preservation of antioxidant defenses, modulation of apoptosis-related gene expression, and structural protection of cardiomyocyte organelles. These findings highlight the potential of GHRP-6 as a therapeutic candidate for mitigating the cardiotoxic and systemic side effects of anthracycline chemotherapy while supporting overall survival [1].

2) This study conducted by researchers Yu et al examined the effects of GHRP-6, on skeletal muscle exposed to doxorubicin. The investigators assessed molecular markers associated with autophagy, apoptosis, insulin-like growth factor signaling, oxidative stress, and histological integrity in skeletal muscle tissue to clarify whether GHRP-6 has protective or modulatory effects under conditions of DOX-induced damage. Several receptor antagonists, including YIL781, TAK-779, and AMD3100, were used to parse the involvement of specific receptor pathways, particularly the CXCR4 receptor, in mediating the observed effects [2].

The study first evaluated autophagic signaling, a cellular recycling process important for maintaining protein and organelle quality control. The ratio of LC3 II-to-LC3 I, a widely recognized marker of autophagosome formation, was found to be significantly elevated following GHRP-6 treatment in both saline- and DOX-treated skeletal muscle, with increases of approximately 400%. This indicates that the compound robustly stimulates autophagy under both normal and toxic conditions. Interestingly, while antagonism of YIL781 and TAK-779 did not interfere with this effect, the administration of AMD3100, a CXCR4 antagonist, markedly reduced the LC3 II-to-LC3 I ratio in DOX-treated muscle co-administered with GHRP-6, suggesting that CXCR4 signaling plays a crucial role in mediating autophagic responses [2].

Beclin-1, a key protein in autophagy initiation, was reduced by 60% in DOX muscle compared to control, indicating impaired autophagic signaling. Treatment with GHRP-6 significantly restored beclin-1 expression by 96% in control muscle and 75% in DOX muscle, confirming its stimulatory effect on the autophagic machinery. This effect was largely abolished by AMD3100 but not by YIL781 or TAK-779, further implicating the CXCR4 pathway. Similar trends were seen with Atg5 protein levels, though these changes did not achieve statistical significance, and no meaningful changes were observed in the Atg12-5 complex. Overall, these findings indicate that GHRP-6 promotes autophagic signaling in skeletal muscle, largely through mechanisms dependent on CXCR4 activity.

Apoptotic signaling, another important determinant of muscle integrity under toxic stress, was also evaluated. DOX treatment significantly increased the apoptotic DNA fragmentation index in skeletal muscle by approximately 100% compared to controls, confirming its pro-apoptotic toxicity. However, co-treatment with GHRP-6 markedly reduced this apoptotic index by about 120% relative to DOX alone, and this protective effect persisted even in the presence of YIL781, TAK-779, or AMD3100. Thus, the anti-apoptotic effect of GHRP-6 appears robust and not dependent on these particular receptor pathways [2].

Regarding pro- and anti-apoptotic protein levels, Bax expression was elevated across all treatment groups relative to control but did not reach significance, while Bcl-2 expression trended higher in all DOX and DOX + GHRP-6 groups but again failed to reach significance. Nonetheless, signaling through Akt and Erk pathways, which are critical for survival signaling, was strongly influenced. DOX reduced phosphorylated Akt/total Akt by 79%, confirming impaired survival signaling. GHRP-6 restored Akt phosphorylation by 80% in both control and DOX-treated muscle, but this effect was significantly reversed by AMD3100, implicating CXCR4 in Akt activation. Erk phosphorylation, reduced by 84% with DOX, was increased by 370% following GHRP-6 treatment, indicating restoration of survival signaling, and this effect was not significantly influenced by the additional antagonists [2].

The study next examined IGF-1, a central anabolic and protective factor in skeletal muscle. DOX dramatically reduced IGF-1 abundance by 70% compared to control, consistent with its catabolic effects. GHRP-6 prevented this reduction and significantly increased IGF-1 abundance by nearly 386% relative to DOX alone. This protective effect was preserved in the presence of YIL781 and TAK-779 but was abolished when AMD3100 was administered, indicating that the IGF-1 restoring effect of GHRP-6 is strongly dependent on CXCR4 signaling.

Oxidative stress was also assessed through markers such as nitrotyrosine and 4-hydroxynonenal. DOX increased nitrotyrosine abundance by 68% compared to controls, reflecting heightened oxidative stress. GHRP-6 partially reduced nitrotyrosine levels by about 30% compared to DOX alone, suggesting modest antioxidant effects. Interestingly, AMD3100 reversed this benefit, producing a 55% increase in nitrotyrosine compared to DOX + GHRP-6, further implicating CXCR4 in regulating oxidative stress. By contrast, no significant changes in 4HNE levels were observed across groups, indicating selective modulation of oxidative stress markers [2].

Histological analysis of skeletal muscle provided further evidence of DOX toxicity and the protective effects of GHRP-6. Normal myofiber morphology was observed in controls, with no abnormalities induced by GHRP-6 alone. DOX caused significant increases in the number of centronucleated myofibers by approximately 150%, reflecting muscle regeneration in response to injury. This pathological increase was prevented by GHRP-6, with or without the tested receptor antagonists. However, no significant differences were noted in muscle fiber size or fiber size distribution across groups, indicating that gross structural preservation was maintained regardless of treatment.

These results demonstrate that GHRP-6 exerts a broad range of protective effects in skeletal muscle exposed to DOX. It robustly stimulates autophagy, restores survival signaling through Akt and Erk pathways, reduces apoptosis, prevents loss of IGF-1, and mitigates certain aspects of oxidative stress. The CXCR4 receptor appears to be critically involved in many of these effects, particularly in regulating autophagy, IGF-1 abundance, Akt phosphorylation, and oxidative stress, as AMD3100 reversed these protective actions. Other receptors, such as those targeted by YIL781 and TAK-779, appeared less involved. Importantly, histological analysis confirmed that GHRP-6 reduced DOX-induced muscle abnormalities without causing any intrinsic damage on its own. Thus, GHRP-6 represents a potential therapeutic agent to counteract muscle toxicity associated with DOX, acting through mechanisms that integrate autophagy, survival signaling, growth factor preservation, and oxidative stress regulation [2].

 

Disclaimer

**LAB USE ONLY**
*This information is for educational purposes only and does not constitute medical advice. THE PRODUCTS DESCRIBED HEREIN ARE FOR RESEARCH USE ONLY. All clinical research must be conducted with oversight from the appropriate Institutional Review Board (IRB). All preclinical research must be conducted with oversight from the appropriate Institutional Animal Care and Use Committee (IACUC) following the guidelines of the Animal Welfare Act (AWA).

 

Citations

[1] Berlanga-Acosta J, Cibrian D, Valiente-Mustelier J, et al. Growth hormone releasing peptide-6 (GHRP-6) prevents doxorubicin-induced myocardial and extra-myocardial damages by activating prosurvival mechanisms. Front Pharmacol. 2024;15:1402138. Published 2024 May 30. doi:10.3389/fphar.2024.1402138.

[2] Yu AP, Pei XM, Sin TK, et al. [D-Lys3]-GHRP-6 exhibits pro-autophagic effects on skeletal muscle. Mol Cell Endocrinol. 2015;401:155-164. doi:10.1016/j.mce.2014.09.031

 

 

GHRP-6 is a growth hormone-releasing peptide that has been shown to release growth hormone (GH) in vivo in several different species. A study conducted by Rico et. Al, studied the effects of GHRP-6 in vitro in bovine somatotropes that were separated through elutriation. GHRP-6 was administered in doses from 10(-8) M to 10(-5)M as well as 10(-9)M in the pituitary cells of the cows. It was found that all doses stimulated the release of GH, however, maximal stimulation of GH was found at 10(-6)M. The effects of treatment with GHRP-6 were seen at hours 1, 2, 3, and 4 of incubation, with the exception of heifer pituitary cells which did not experience the effects at hour 1 of the incubation period (https://pubmed.ncbi.nlm.nih.gov/10494658/).

 

Effects of GHRP-6 in Preventing Cardiovascular Failure

Several studies in mice conducted from 1997 to 1999 examined the role that growth hormone-releasing peptides played in preventing heart failure. These studies were limited due to technology and resources but came to the general conclusion that GHRPs were able to prevent cardiovascular failure.

In more recent studies DCM models characterized by left ventricle dilation, wall thinning, and systolic dysfunction examine how GHRP-6 was able to combat the declining function of the left ventricle. Rats were administered doxorubicin (DX) in order to induce a DCM model of heart failure. Overall, the study found that rats treated with GHRP-6 experienced a complete prevention of heart failure and decreased mortality rate among the rats.

While it is still difficult to determine exactly why GHRP-6 is able to prevent heart failure and increase survival rate, a report by Merck Research Laboratories theorized that this occurred due to the mediation of Ca2+. When Ca2+ is triggered to release from intracellular stores there is a resulting positive inotropic effect without the possibility of eliciting a drastic change in heart rate.

 

GHRP-6 and Heart Health

Furthermore, a study conducted by Berlanga-Acosta et. Al, treated both infarcted and healthy rabbits with GHRP-6 in order to examine the effects the peptide had on the heart. Researchers treated the rabbits with 400 microg/kg of GHRP-6 through an intravenous bolus. Similar to the theory mentioned above, it was found that treatment with GHRP-6 led to a positive and transient inotropic effect on the cardiac muscle. Additionally, the study showed that when treated with GHRP-6 the ejection fraction increased by 15-20% which was confirmed through the use of echocardiography.

Belanga-Acosta et. Al conducted a similar study using porcine models that had undergone acute myocardial infarction caused by blocking the left circumflex artery. The subjects were then reperfused over a 72-hour period and it was shown that the treatment led to a reported repair of the damaged myocardium (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5392015/)

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