Roh S G, He M L, Matsunaga N, Hidaka S, Hidari H
Department of Animal Science, Obihiro University of Agriculture and Veterinary Medicine, Japan.
J Anim Sci. 1997 Oct;75(10):2749-53. doi: 10.2527/1997.75102749x.
We investigated the desensitization caused by growth hormone (GH)-releasing peptide-2 (D-Ala-D-beta Nal-Ala-Trp-D-Phe-Lys-NH2; GHRP-2) in vivo using calves. The GHRP-2 (12.5 micrograms.kgBW-1.h-1) or GH-releasing factor (GRF; .125 microgram.kgBW-1.h-1) were infused for 180 min into four calves, each followed by either GHRP-2 (12.5 micrograms/kg BW) or GRF (.125 microgram/kg BW) injection after 60 min. All treatments were given to all of the calves. The continuous infusion of GHRP-2 did not attenuate the GH secretion caused by a GRF bolus, and vice versa. Continuous exposure to GHRP-2 attenuated the GH secretion caused by a GHRP-2 bolus. In an additional experiment, two repetitive injections of GHRP-2 (12.5 micrograms/kg BW) at 1-, 2-, 3-, or 4-h intervals were administered. Attenuation of the GH response caused by GHRP-2 was maintained until 4 h. These results suggest that GHRP-2 is not cross-desensitized with GRF and that the mechanisms by which they cause GH release may be different in calves.
我们使用小牛在体内研究了生长激素（GH）释放肽-2（D-丙氨酸-D-β-萘基丙氨酸-丙氨酸-色氨酸-D-苯丙氨酸-赖氨酸-NH2；GHRP-2）引起的脱敏作用。将GHRP-2（12.5微克·千克体重-1·小时-1）或生长激素释放因子（GRF；0.125微克·千克体重-1·小时-1）持续输注180分钟给4头小牛，每头小牛在60分钟后分别注射GHRP-2（12.5微克/千克体重）或GRF（0.125微克/千克体重）。所有处理对所有小牛都进行了。持续输注GHRP-2并未减弱GRF推注引起的GH分泌，反之亦然。持续暴露于GHRP-2会减弱GHRP-2推注引起的GH分泌。在另一项实验中，以1、2、3或4小时间隔重复两次注射GHRP-2（12.5微克/千克体重）。GHRP-2引起的GH反应减弱一直维持到4小时。这些结果表明，GHRP-2与GRF不存在交叉脱敏，并且它们在小牛中引起GH释放的机制可能不同。
