Bagna B, Schwabe C, Anderson L L
Department of Animal Science, Iowa State University, Ames 50011.
J Reprod Fertil. 1991 Mar;91(2):605-15. doi: 10.1530/jrf.0.0910605.
Purified pig relaxin (3000 U/mg) was injected i.m. into pregnant Holstein dairy heifers on Day 276 or 277 to determine its effect on parturition and sequential measurements of the pelvic area, cervical dilatation, and peripheral blood-plasma concentrations of progesterone and relaxin. Treatments included phosphate-buffer saline (2 ml, Group C, N = 7), relaxin once (1 mg, Group 1R, N = 7), and twice (2 mg, 12 h apart; Group 2R, N = 7). Intervals (mean +/- s.e.) between the first injection of relaxin or PBS and calving were 64 +/- 17, 80 +/- 19 and 125 +/- 34 h for Groups 2R, 1R and C, respectively. The calving intervals were reduced in Groups 2R (P less than 0.01) and 1R (P less than 0.05) compared with Group C. The incidence of dystocia was 29% (2 of 7) in Group 2R and 43% (3 of 7) in Group 1R compared with 57% (4 of 7) in Group C (P less than 0.01). Body weights and ratios of males to females of the calves were similar (P greater than 0.05) between groups. Progesterone plasma concentrations decreased (P less than 0.01) earlier in Groups 1R and 2R compared with Group C, and this acute decrease began within 6 h of treatment. At 24 h after relaxin or PBS injection, progesterone concentrations were 2.7 +/- 1.1 ng/ml for Group 2R, 3.5 +/- 0.9 ng/ml for Group 1R, and 6.0 +/- 0.1 ng/ml for Group C. Relaxin reached peak blood-plasma levels of 19 +/- 2.2 ng/ml 1 h after injection of relaxin, but remained unchanged, 0.3 +/- 0.01 ng/ml, in Group C. Pelvic area was increased 26%, 22% and 14% and cervical dilatation was increased 109%, 76% and 53% 48 h after injection in Groups 2R, 1R and C, respectively, but these responses were similar among groups at the time of parturition. We conclude that two i.m. injections of relaxin facilitated earlier calving, acutely decreased progesterone secretion, increased cervical dilatation and pelvic area expansion, and decreased the incidence of dystocia in dairy heifers.
将纯化的猪松弛素（3000 U/mg）于妊娠第276天或277天肌肉注射到怀孕的荷斯坦奶牛小母牛体内，以确定其对分娩的影响以及对骨盆区域、宫颈扩张以及外周血血浆中孕酮和松弛素浓度的连续测量结果。治疗组包括磷酸盐缓冲盐水（2 ml，C组，n = 7）、单次注射松弛素（1 mg，1R组，n = 7）和两次注射松弛素（2 mg，间隔12小时；2R组，n = 7）。2R组、1R组和C组从首次注射松弛素或PBS到产犊的间隔时间（平均值±标准误）分别为64±17、80±19和125±34小时。与C组相比，2R组（P<0.01）和1R组（P<0.05）的产犊间隔时间缩短。2R组难产发生率为29%（7头中的2头），1R组为43%（7头中的3头），而C组为57%（7头中的4头）（P<0.01）。各组间犊牛的体重和雌雄比例相似（P>0.05）。与C组相比，1R组和2R组血浆孕酮浓度下降更早（P<0.01），且这种急性下降在治疗后6小时内开始。在注射松弛素或PBS后24小时，2R组孕酮浓度为2.7±1.1 ng/ml，1R组为3.5±0.9 ng/ml，C组为6.0±0.1 ng/ml。注射松弛素1小时后，松弛素达到血浆峰值水平19±2.2 ng/ml，但在C组中保持不变，为0.3±0.01 ng/ml。注射后48小时，2R组、1R组和C组的骨盆区域分别增加26%、22%和14%，宫颈扩张分别增加109%、76%和53%，但在分娩时这些反应在各组间相似。我们得出结论，两次肌肉注射松弛素可促进奶牛小母牛提前产犊，急性降低孕酮分泌，增加宫颈扩张和骨盆区域扩张，并降低难产发生率。
