Tallam S K, Walton J S, Johnson W H
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
Theriogenology. 2000 Mar 1;53(4):951-62. doi: 10.1016/S0093-691X(00)00242-9.
Holstein heifers were used to study effects of exogenous administration of oxytocin on luteal function and ovarian follicular development. Twelve heifers were monitored for 1 estrous cycle to confirm normal ovarian function. At the subsequent estrus, these animals were randomly assigned to 1 of 3 treatments: saline control, (Group 1, n=4), oxytocin (Group 2, n=4) and saline pregnant (Group 3, n=4). Group 2 received continuous infusion of oxytocin (1.9 mg/d) from Days 14 to 26 after estrus, while Groups 1 and 3 received saline infusion during the same period. Group 3 were artificially inseminated at estrus. Daily blood samples were collected for oxytocin and progesterone assay. Ovarian follicles and corpus luteum (CL) development were monitored daily by transrectal ultrasonography until Day 32 after estrus. Plasma progesterone (P4) concentrations prior to initiation of infusion were 7.6+/-1.3 ng/mL on Day 14. They then decreased to <1 ng/mL on Day 19 for Group 1 and on Day 28 for Group 2. The interestrous interval was longer (P <0.05) for heifers that received oxytocin infusion. During the infusion period P4 concentrations were not different (P >0.05) between Group 2 and 3 but declined gradually from Day 20 in Group 2 despite the presence of high plasma oxytocin concentrations. Control heifers had 2 waves of follicular growth, with the second dominant follicle ovulating. Three of the 4 oxytocin-infused animals had an additional wave, with the third dominant follicle ovulating. Oxytocin infusion had no effect on size of the ovulating follicle (P >0.05) and the number of Class 1 follicles (3 to 5 mm, P >0.1). Differences in the number of Class 2 follicles (6 to 9 mm) among treatments on Days 15 to 22 after estrus were not detected (P >0.1) except on Days 23 to 26, when Group 2 had fewer follicles than Group 3 (P <0.05). The results show that continuous infusion of oxytocin during normal luteolysis delays luteal regression without inhibiting follicular development.
选用荷斯坦小母牛来研究外源性给予催产素对黄体功能和卵泡发育的影响。监测12头小母牛1个发情周期，以确认其卵巢功能正常。在随后的发情期，将这些动物随机分为3组进行处理：生理盐水对照组（第1组，n = 4）、催产素组（第2组，n = 4）和生理盐水妊娠组（第3组，n = 4）。第2组在发情后第14至26天持续输注催产素（1.9 mg/d），而第1组和第3组在同一时期输注生理盐水。第3组在发情期进行人工授精。每天采集血样进行催产素和孕酮检测。通过经直肠超声检查每天监测卵泡和黄体（CL）的发育，直至发情后第32天。输注开始前，第14天血浆孕酮（P4）浓度为7.6±1.3 ng/mL。然后，第1组在第19天、第2组在第28天降至<1 ng/mL。接受催产素输注的小母牛发情间期更长（P<0.05）。在输注期间，第2组和第3组之间的P4浓度无差异（P>0.05），但尽管血浆催产素浓度较高，第2组从第20天起P4浓度仍逐渐下降。对照小母牛有2个卵泡生长波，第二个优势卵泡排卵。4头接受催产素输注的动物中有3头有额外的卵泡波，第三个优势卵泡排卵。催产素输注对排卵卵泡大小（P>0.05）和1类卵泡数量（3至5 mm，P>0.1）无影响。除了在发情后第23至26天，第2组的卵泡数量少于第3组（P<0.05）外，在发情后第15至22天各处理组之间2类卵泡（6至9 mm）数量的差异未被检测到（P>0.1）。结果表明，在正常黄体溶解过程中持续输注催产素可延迟黄体退化，而不抑制卵泡发育。
