Cochran R A, Leonardi-Cattolica A A, Sullivan M R, Kincaid L A, Leise B S, Thompson D L, Godke R A
Department of Animal Science, Louisiana State University, Baton Rouge 70803, USA.
Domest Anim Endocrinol. 1999 Jan;16(1):57-67. doi: 10.1016/s0739-7240(98)00046-0.
The effects of exogenous equine somatotropin (eST) administration on ovarian activity and plasma hormone levels were evaluated on horse and pony mares. The objectives of this study were to determine the effects of eST on follicular development and circulating concentrations of leutinizing hormone (LH), estradiol, progesterone, and insulin-like growth factor I (IGF-I) in cyclic horse and pony mares. Sixteen mares received daily injections (i.m.) of eST at a concentration of 25 micrograms/kg body weight on either Days 6 through 12 (Treatment A) or 13 through 19 (Treatment B) postovulation. In addition, contemporary mares were similarly given the carrier vehicle and served as controls (Treatments C and D). Blood samples were collected at 24-hr intervals and ultrasonographic evaluations were performed on the ovaries of each mare at 48-hr intervals beginning on the first day of treatment and ending either on the day of ovulation or 5 d postovulation. Circulating levels of insulin-like growth factor-I (IGF-I) were increased in treated mares by Day 3 post-treatment (P < 0.05). Also, mares in Treatment B exhibited a decrease in plasma estradiol concentrations (P < 0.05) when compared with control mares on Days 1 through 5 postovulation of the post-treated estrous cycle. In addition, circulating leutinizing hormone levels were different for mares in Treatment A compared with controls on Days--8 through--1 pre-ovulation (P < 0.05). All follicles present on the ovaries of each mare were measured and placed into one of five categories based on their diameter. Neither the mean number of follicles per size category > or = 8 mm in diameter nor the mean follicular diameter within each size category differed among treatment and control mares. However, eST treatment significantly increased the number of follicles < or = 7 mm on the ovaries of mares treated early in the estrous cycle when compared with control mares on Days 3 and 7 post-treatment and at the onset of standing estrus.
对外源马生长激素（eST）给药对母马和小母马卵巢活动及血浆激素水平的影响进行了评估。本研究的目的是确定eST对周期性母马和小母马卵泡发育以及促黄体生成素（LH）、雌二醇、孕酮和胰岛素样生长因子I（IGF-I）循环浓度的影响。16匹母马在排卵后第6至12天（处理A）或第13至19天（处理B）每天接受浓度为25微克/千克体重的eST肌肉注射。此外，同期母马同样注射载体溶液并作为对照（处理C和D）。从治疗第一天开始，每隔24小时采集一次血样，每隔48小时对每匹母马的卵巢进行超声检查，检查持续到排卵日或排卵后5天。治疗后第3天，治疗组母马的胰岛素样生长因子-I（IGF-I）循环水平升高（P<0.05）。此外，与对照母马相比，处理B组的母马在处理后的发情周期排卵后第1至5天血浆雌二醇浓度降低（P<0.05）。此外，在排卵前第8天至第1天，处理A组母马的促黄体生成素循环水平与对照组不同（P<0.05）。测量每匹母马卵巢上所有卵泡的大小，并根据直径将其分为五类。处理组和对照组母马中，直径≥8毫米的每个大小类别卵泡的平均数量以及每个大小类别内的平均卵泡直径均无差异。然而，与对照母马相比，在发情周期早期接受治疗的母马卵巢上直径≤7毫米的卵泡数量在治疗后第3天、第7天以及发情站立开始时显著增加。
