Shepherd B S, Eckert S M, Parhar I S, Vijayan M M, Wakabayashi I, Hirano T, Grau E G, Chen T T
Biotechnology Center, University of Connecticut, Storrs, Connecticut 06269, USA.
J Endocrinol. 2000 Dec;167(3):R7-10. doi: 10.1677/joe.0.167r007.
Abstract Studies in mammals have shown that synthetic Met-enkephalin derivatives, called growth hormone-releasing peptides (GHRPs), stimulate growth hormone (GH) release. The present study was conducted to determine whether the GHRP, KP-102, specifically stimulates GH release in a teleost. Tilapia (Oreochromis mossambicus) were given a single intraperitoneal injection of KP-102 (D-Ala-D-beta;-Nal-Ala-Trp-D-Phe-Lys-NH(2)) or bovine GHRH(1-29)-amide or vehicle and blood was sampled at 1, 6 and 12 h after injection. KP-102 was administered at two doses of 1 ng/g and 10 ng/g body weight, whereas GHRH (positive control) was administered at a single dose of 10 ng/g body weight. Plasma levels of tilapia GH and prolactins (tPRL(177) and tPRL(188)) were determined by radioimmunoassay. As expected, GHRH injection significantly (P<0.001) elevated plasma GH levels (ng/ml) in tilapia at 6 h post-injection. KP-102 also significantly elevated GH levels (at the low dose) at 6 (P<0.05) and 12 (P<0.01) hours post-injection. There were no significant effects on plasma PRL(s) levels, although mean levels of both PRLs were elevated at 6 h post-injection. These results show for the first time that GHRPs stimulate GH release in teleosts and suggest that the GHRP receptor and possibly a "Ghrelin-like" ligand are also present in lower vertebrates.
摘要 对哺乳动物的研究表明，名为生长激素释放肽（GHRPs）的合成甲硫氨酸脑啡肽衍生物能刺激生长激素（GH）释放。本研究旨在确定GHRP，即KP-102，是否能特异性刺激硬骨鱼的GH释放。给罗非鱼（莫桑比克罗非鱼）腹腔内单次注射KP-102（D-丙氨酸-D-β-萘丙氨酸-丙氨酸-色氨酸-D-苯丙氨酸-赖氨酸-NH₂）或牛生长激素释放激素（1-29）酰胺或赋形剂，并在注射后1、6和12小时采集血液样本。KP-102以1 ng/g和10 ng/g体重的两种剂量给药，而生长激素释放激素（阳性对照）以10 ng/g体重的单一剂量给药。通过放射免疫分析法测定罗非鱼生长激素和催乳素（tPRL₁₇₇和tPRL₁₈₈）的血浆水平。正如预期的那样，注射生长激素释放激素在注射后6小时显著（P<0.001）提高了罗非鱼的血浆生长激素水平（ng/ml）。KP-102在注射后6小时（P<0.05）和12小时（P<0.01）也显著提高了生长激素水平（低剂量时）。对血浆催乳素水平没有显著影响，尽管两种催乳素的平均水平在注射后6小时有所升高。这些结果首次表明GHRPs能刺激硬骨鱼的生长激素释放，并表明GHRP受体以及可能的“胃饥饿素样”配体在低等脊椎动物中也存在。
