Plouzek C A, Vale W, Rivier J, Anderson L L, Trenkle A
Department of Animal Science, Iowa State University, Ames 50011.
Proc Soc Exp Biol Med. 1988 Jun;188(2):198-205. doi: 10.3181/00379727-188-42728.
The effects of iv administration of growth hormone-releasing factor (GRF) on growth hormone (GH) release and on nitrogen metabolism were measured in prepubertal calves. Crossbred beef heifers (111 kg) were used in a Latin square design to test the effects of 0, 0.01, 0.033, 0.067, and 0.1 microgram human pancreatic (hp) GRF [hpGRF (1,40)OH]/kg body wt on plasma GH concentrations. When they were given doses of 0.067 and 0.1 microgram hpGRF/kg body wt, plasma GH increased (P less than 0.05) within 5-15 min, compared with injections of control buffer, and then returned to preinjection concentrations. The response to 0.067 microgram hpGRF/kg body wt every 3 hr for 42 hr was studied in five heifers (137 kg body wt). The animals responded to 50% of the GRF injections with an increase in plasma GH during every 6-hr period measured. Nitrogen retention, hormone concentrations, and weight gain were measured in five bull calves (90 kg body wt) administered 0 or 0.067 microgram Nle rat hypothalamic GRF (1,29)NH2/kg body wt every 4 hr for 10 days. Metabolic parameters were interpreted to indicate an anabolic response to GRF even though increases of 16% in nitrogen retention, 23% in plasma somatomedin C concentrations, and 36% in weight gain with pulsatile GRF treatment were variable and statistically similar to those of controls. These results indicate that GRF induces peak GH secretion within 15 min in prepubertal calves and that calves can respond to multiple injections of GRF with an increase in plasma GH.
在青春期前的犊牛中，测定了静脉注射生长激素释放因子（GRF）对生长激素（GH）释放及氮代谢的影响。采用拉丁方设计，使用杂交肉用小母牛（体重111千克）来测试0、0.01、0.033、0.067和0.1微克人胰腺（hp）GRF [hpGRF(1,40)OH]/千克体重对血浆GH浓度的影响。当给予0.067和0.1微克hpGRF/千克体重的剂量时，与注射对照缓冲液相比，血浆GH在5 - 15分钟内升高（P<0.05），然后恢复到注射前浓度。对5头小母牛（体重137千克）每3小时注射0.067微克hpGRF/千克体重，共注射42小时，研究其反应。在每6小时的测量期间，动物对50%的GRF注射有血浆GH升高的反应。对5头公牛犊（体重90千克）每4小时给予0或0.067微克Nle大鼠下丘脑GRF(1,29)NH2/千克体重，持续10天，测量氮潴留、激素浓度和体重增加情况。代谢参数被解释为表明对GRF有合成代谢反应，尽管脉冲式GRF治疗使氮潴留增加16%、血浆生长调节素C浓度增加23%、体重增加36%，但这些变化具有变异性且在统计学上与对照组相似。这些结果表明，GRF在青春期前犊牛中15分钟内诱导GH分泌峰值，且犊牛对多次注射GRF有血浆GH升高的反应。
