Characteristics of growth hormone secretion responsiveness to growth hormone-releasing peptide-2 (GHRP-2 or KP102) in calves.
Roh. S G SG; Matsunaga. N N; Hidaka. S S; Hidari. H H
Key Findings
- Acute GHRP‑2 injections (6.25‑25 µg/kg) sharply increased GH secretion for about an hour.
- Repeated injections every 2 hours caused the GH response to drop dramatically after the first dose.
- Continuous low‑dose infusion for 14 days raised average daily weight gain by ~36% without a sustained rise in plasma GH, but IGF‑1 tended to be higher.
Practical Outcomes
- For biohackers, the data suggest that GHRP‑2 can trigger a strong, short‑lived GH spike, but the body quickly becomes tolerant to repeated dosing. Continuous low‑dose delivery might improve growth‑related outcomes via IGF‑1 rather than sustained GH elevation. However, because the study was done in calves, direct translation to human protocols is uncertain and would require careful dosing trials.
Summary
In young male calves, a single injection of the growth hormone‑releasing peptide GHRP‑2 boosted blood GH levels in a dose‑dependent way, but repeated doses quickly reduced the response. Over two weeks, a continuous low‑dose infusion of GHRP‑2 didn’t raise GH much but did increase growth (weight gain) and hinted at higher IGF‑1, a downstream growth factor.
Abstract
This study was conducted to determine the effects of acute and chronic administration of GH-releasing peptide-2 (D-Ala-D-beta Nal-Ala-Trp-D-Phe-Lys-NH2, GHRP-2 or KP102) on GH responsiveness in male Holstein calves. In the dose response study of acute administration, six calves were injected iv with saline or 6.25, 12.5 and 25.0 micrograms/kg body weight (BW) of KP102. The GH AUC (area under curve, ng/ml.min, mean +/- SEM) for 60 min was significantly increased with 6.25 (676.3 +/- 125.6), 12.5 (1574.8 +/- 318.0) and 25.0 (1578.7 +/- 214.6) micrograms/kgBW of KP102 than with saline (78.6 +/- 36.1) (P < 0.01). GH responses were decreased by multiple injections of 12.5 micrograms/kgBW KP102 at every 2 h for 8 h. The GH AUC for 60 min was decreased from the first injection (1162.9 +/- 313.3) to the second injection (604.7 +/- 131.9), but the response was significantly higher for the first and second injections than the third (304.4 +/- 173.1) and fourth injections (320.7 +/- 144.2) (P < 0.05). In the chronic administration, 8 calves were implanted subcutaneously with osmotic pumps (Alzet pump). Each of the 4 calves was given with 12.5 micrograms/kgBW per hour KP102 and the other 4 calves served as the control. During the 14 day period, average daily gain was significantly increased (36.4%) over the control (P < 0.05). Food efficiency was not significant, but numerically higher (29.4%) than the control. The plasma GH concentration was not increased by chronic administration of KP102, but IGF-I appeared to increase in KP102-treated calves more than the control. These results suggest that the synthetic KP102 can be used for enhancing the growth performance in domestic animals.
Study Information
pubmed
1996
10.1507/endocrj.43.291