Hashizume T, Ohtsuki K, Sasaki K, Yanagimoto M, Masuda H, Hirata T, Ohashi S
Laboratory of Animal Breeding and Reproduction, Faculty of Agriculture, Iwate University, Morioka, Japan.
Endocr J. 1997 Dec;44(6):811-7. doi: 10.1507/endocrj.44.811.
Effects of bovine and human growth hormone-releasing hormone (GRF) analogs (bGRF(1-29)-NH2: bGRF-29, [D-Ala2, Ala15]-bGRF-29, [D-Ala2]-hGRF(1-29)-NH2: [D-Ala2]-hGRF-29), bovine GRF (bGRF(1-44)-NH2: bGRF-44), as well as rat GRF (rGRF) on GH release were studied in female calves. Intravenous (i.v.) bolus injections of 0.25 microg/kg BW of bGRF-29, [D-Ala2, Ala15]-bGRF-29, and [D-Ala2]-hGRF-29 stimulated GH release. Plasma GH levels began to rise 10 min after the injection of each peptide, and significant increases in GH concentrations were obtained at 60, 180 and 150 min after the injection of bGRF-29, [D-Ala2, Ala15]-bGRF-29 and [D-Ala2]-hGRF-29, respectively. The concentrations of GH 80 min after the injection of [D-Ala2, Ala15]-bGRF-29 were significantly higher than those after the injection of [D-Ala2]-hGRF-29 (except at 80 and 90 min) or bGRF-29. The i.v. bolus injections of 0.25 microg/kg BW of bGRF-44 and rGRF stimulated GH release, and the GH-releasing potency of rGRF was approximately equal to that of bGRF-44. The plasma GH responses to the repeated i.v. injection of bGRF-29 or [D-Ala2, Ala15]-bGRF-29 at 2-h intervals were examined. bGRF-29 acutely increased plasma GH levels after each injection, and the high GH levels decreased to the basal values within 2 h. In contrast, high GH levels induced by [D-Ala2, Ala15]-bGRF-29 were gradually decreased but not lowered to basal values throughout the experiment. These results show that [D-Ala2, Ala15]-bGRF-29 has longer-lasting and greater GH-releasing activity than the other GRF analogs in female calves, and the GH-releasing potency of rat GRF is approximately equal to that of bovine GRF in cattle in vivo.
研究了牛和人生长激素释放激素（GRF）类似物（bGRF(1 - 29)-NH2：bGRF - 29、[D - Ala2, Ala15]-bGRF - 29、[D - Ala2]-hGRF(1 - 29)-NH2：[D - Ala2]-hGRF - 29）、牛GRF（bGRF(1 - 44)-NH2：bGRF - 44）以及大鼠GRF（rGRF）对雌性犊牛生长激素（GH）释放的影响。静脉推注0.25μg/kg体重的bGRF - 29、[D - Ala2, Ala15]-bGRF - 29和[D - Ala2]-hGRF - 29可刺激GH释放。注射每种肽后10分钟血浆GH水平开始升高，注射bGRF - 29、[D - Ala2, Ala15]-bGRF - 29和[D - Ala2]-hGRF - 29后，分别在60、180和150分钟时GH浓度显著升高。注射[D - Ala2, Ala15]-bGRF - 29后80分钟时的GH浓度显著高于注射[D - Ala2]-hGRF - 29（80和90分钟除外）或bGRF - 29后的浓度。静脉推注0.25μg/kg体重的bGRF - 44和rGRF可刺激GH释放，rGRF的GH释放效力与bGRF - 44大致相当。研究了以2小时间隔重复静脉注射bGRF - 29或[D - Ala2, Ala15]-bGRF - 29后血浆GH的反应。每次注射bGRF - 29后可使血浆GH水平急性升高，且高GH水平在2小时内降至基础值。相比之下，[D - Ala2, Ala15]-bGRF - 29诱导的高GH水平逐渐下降，但在整个实验过程中未降至基础值。这些结果表明，在雌性犊牛中，[D - Ala2, Ala15]-bGRF - 29比其他GRF类似物具有更持久且更强的GH释放活性，并且在体内牛中大鼠GRF的GH释放效力与牛GRF大致相当。
