Thatcher C E, Thompson D L
Department of Animal Science, Louisiana Agricultural Experiment Station, LSU Agricultural Center, Baton Rouge, LA, USA.
Domest Anim Endocrinol. 2002 May;22(3):127-43. doi: 10.1016/s0739-7240(02)00120-0.
Two experiments compared the efficacies of different treatment frequencies for recombinant equine somatotropin (eST). In Experiment 1, five geldings received daily injections of eST at 20 microg/kg of body weight, and five received every-other-day injections at 40 microg/kg of body weight, for a total of 30 days. Plasma glucose (P=0.0001), insulin (P=0.0135), and non-esterified fatty acid (NEFA, P=0.0001) concentrations increased, and plasma urea nitrogen (PUN) concentrations decreased (P=0.0001), in both groups, and only minor differences (P<0.05) occurred between the two groups. Insulin-like growth factor-I (IGF-I) concentrations increased (P=0.0001) in both groups over time, and were higher (P<0.05) after day 2 in geldings treated daily. Endogenous somatotropin (ST) response to secretagogue was inhibited (P<0.05) in geldings receiving daily injections relative to those receiving every-other-day injections. In Experiment 2, 16 geldings were allotted to four groups of four. A control group received daily saline injections, and the other three groups received eST at 20 microg/kg of body weight daily as a single injection, two injections (every 12h), or four injections (every 6h), for a total of 14 days. Plasma IGF-I and insulin concentrations increased (P<0.05) in all groups receiving eST, with the responses being proportional to injection frequency. In contrast, PUN concentrations decreased (P<0.05) in all groups equally. In conclusion, the efficacy of daily versus every-other-day injections of eST depends upon the response to be measured, and for IGF-I concentrations, the every-other-day regimen was not acceptable. Injection frequencies greater than once daily were more efficacious for IGF-I and insulin concentrations, but not for PUN concentrations. Thus, the optimum injection regimen for any new application for eST cannot simply be inferred from other biological responses, and will need to be determined empirically.
两项实验比较了重组马生长激素（eST）不同治疗频率的疗效。在实验1中，五匹去势公马每天接受20微克/千克体重的eST注射，另外五匹每隔一天接受40微克/千克体重的注射，共30天。两组的血浆葡萄糖（P = 0.0001）、胰岛素（P = 0.0135）和非酯化脂肪酸（NEFA，P = 0.0001）浓度均升高，血浆尿素氮（PUN）浓度降低（P = 0.0001），两组之间仅存在微小差异（P<0.05）。随着时间的推移，两组的胰岛素样生长因子-I（IGF-I）浓度均升高（P = 0.0001），且在每天接受治疗的去势公马中，第2天后IGF-I浓度更高（P<0.05）。与每隔一天注射的去势公马相比，每天注射的去势公马中内源性生长激素（ST）对促分泌素的反应受到抑制（P<0.05）。在实验2中，16匹去势公马被分为四组，每组四匹。一个对照组每天接受生理盐水注射，其他三组每天接受20微克/千克体重的eST注射，分别为单次注射、两次注射（每12小时一次）或四次注射（每6小时一次），共14天。所有接受eST治疗的组中，血浆IGF-I和胰岛素浓度均升高（P<0.05），且反应与注射频率成正比。相比之下，所有组的PUN浓度均同等程度降低（P<0.05）。总之，每天注射与每隔一天注射eST的疗效取决于所测量的反应，对于IGF-I浓度而言，每隔一天的治疗方案不可接受。每天注射频率大于一次对于IGF-I和胰岛素浓度更有效，但对PUN浓度无效。因此，eST任何新应用的最佳注射方案不能简单地从其他生物学反应中推断出来，而需要通过实验确定。
