Bartlewski P M, Vanderpol J, Beard A P, Cook S J, Rawlings N C
Department of Veterinary Physiological Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada.
Anim Reprod Sci. 2000 Mar 15;58(3-4):273-91. doi: 10.1016/s0378-4320(99)00092-5.
Daily transrectal ultrasonography of ovaries was done in seven Finn ewes during three 17-day periods from May to July. Blood samples were collected each day for estimation of the serum follicle-stimulating hormone (FSH), oestradiol and progesterone concentrations, and also every 15 min for 6 h, halfway through each period of ultrasonographic examination, to determine the patterns of gonadotropic hormone secretion. Four ewes ceased cycling from March to mid-April (ewes entering anoestrus early) and three in May (ewes entering anoestrus late). In all ewes cyclicity resumed during the period from mid-August to mid-September. The growth of ovarian antral follicles to periovulatory sizes of >/=5 mm in diameter was seen at all stages of anoestrus. An average of four waves of follicular development (follicles growing from 3 to >/=5 mm in diameter before regression) with a periodicity of 4 days were recorded during each of the three scanning periods. There was a close temporal relationship between days of follicular wave emergence and peaks of successive FSH fluctuations. Ewes entering anoestrus late exceeded ewes that became anoestrus early in numbers of large (>/=5 mm in diameter) ovarian antral follicles and maximum follicle diameter. Peak concentrations of transient FSH increases were higher (P<0.05) in ewes entering anoestrus late than in ewes entering anoestrus early. The secretion of luteinising hormone, (LH; mean and basal level, and LH pulse frequency, but not amplitude) was lowest during the month of June in all ewes. Oestradiol production was markedly suppressed throughout anoestrus. Peaks of progesterone secretion appeared to occur at regular intervals and were associated with the end of the growth phase of the largest follicles of sequential waves. In conclusion, the growth of ovarian follicles to ostensibly ovulatory diameters is maintained throughout anoestrus in Finn ewes and periodic emergence of follicular waves is correlated with an endogenous rhythm of FSH secretion. The present study also provides evidence for the inverse relationship between the time of the onset of seasonal anoestrus and the number and size of antral follicles developing throughout anoestrus in Finn ewes, and indicates that differences exist in both the secretion of and ovarian responsiveness to gonadotropic hormones among early and late anoestrous ewes.
在5月至7月的三个17天期间，对7只芬兰母羊进行了每日经直肠卵巢超声检查。每天采集血样以测定血清促卵泡激素（FSH）、雌二醇和孕酮浓度，并且在每个超声检查期的中间时段，每隔15分钟采集6小时血样，以确定促性腺激素的分泌模式。4只母羊在3月至4月中旬停止发情（早期进入乏情期的母羊），3只在5月停止发情（晚期进入乏情期的母羊）。在所有母羊中，发情周期在8月中旬至9月中旬恢复。在乏情期的所有阶段都可见卵巢窦卵泡生长至直径≥5mm的排卵前大小。在三个扫描期的每个期间，平均记录到四波卵泡发育（卵泡在退化前从3mm生长至直径≥5mm），周期为4天。卵泡波出现的天数与连续FSH波动的峰值之间存在密切的时间关系。晚期进入乏情期的母羊在大（直径≥5mm）卵巢窦卵泡数量和最大卵泡直径方面超过早期进入乏情期的母羊。晚期进入乏情期的母羊中短暂FSH升高的峰值浓度高于早期进入乏情期的母羊（P<0.05）。在所有母羊中，6月份促黄体生成素（LH；平均水平和基础水平，以及LH脉冲频率，但不包括幅度）的分泌最低。在整个乏情期，雌二醇的产生明显受到抑制。孕酮分泌峰值似乎有规律地出现，并且与连续波中最大卵泡生长阶段的结束相关。总之，芬兰母羊在整个乏情期卵巢卵泡生长至明显的排卵直径得以维持，卵泡波的周期性出现与FSH分泌的内源性节律相关。本研究还为芬兰母羊季节性乏情开始时间与整个乏情期发育的窦卵泡数量和大小之间的反比关系提供了证据，并表明早期和晚期乏情母羊在促性腺激素分泌和卵巢对促性腺激素的反应性方面均存在差异。
