Voss A K, Fortune J E
Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca 14853.
Endocrinology. 1991 Apr;128(4):1991-9. doi: 10.1210/endo-128-4-1991.
Oxytocin (OT) has been detected in ruminant preovulatory follicles. Bovine granulosa cells express the oxytocin/neurophysin I (OT/NP-I) gene and secrete OT in vitro. The objective of this study was to determine the developmental pattern of OT secretion by bovine follicle cells as they differentiate during the follicular phase and the preovulatory follicle approaches ovulation. Holstein heifers were injected with prostaglandin F2 alpha in midluteal phase to induce luteal regression and initiate a follicular phase. The ovary bearing the preovulatory follicle was obtained by ovariectomy early in the follicular phase, in midfollicular phase, or late in the follicular phase, after the LH/FSH surge (n = 4 heifers per group). Theca interna and granulosa cells were isolated and cultured for 5 days, individually or in coculture, in defined or serum-containing medium and with or without LH (300 ng/ml) or FSH (300 ng/ml). Media were collected and replaced completely every 24 h, and OT secreted into the media was measured by RIA. Granulosa cells isolated at all three time points during the follicular phase secreted measurable amounts of OT. However, total OT secretion by granulosa cells isolated after the LH/FSH surge was 18.9-fold (defined medium) to 64.8-fold (serum-containing medium) higher than OT secretion by granulosa cells isolated early in the follicular phase, and 14.6-fold (defined medium) to 170-fold (serum-containing medium) higher than OT secretion by granulosa cells isolated in midfollicular phase. Granulosa cells isolated before the LH/FSH surge responded to the addition of LH or FSH to the culture medium with an increase in OT secretion. Cocultures of granulosa cells and theca interna isolated before the LH surge secreted more OT than cultures of granulosa cells alone. When cells were isolated early in the follicular phase the effect of coculture was more than additive, but the effect of coculture was only additive when follicles were obtained in midfollicular phase. OT secretion by granulosa cells isolated after the LH/FSH surge was not affected by gonadotropins or by coculture with theca interna. In contrast to results for granulosa cells, theca interna secreted only small and variable amounts of OT, and responses to LH were inconsistent. These findings suggest that OT detected in cultures of theca interna may be produced by small and variable numbers of granulosa cells contaminating the theca interna preparation.(ABSTRACT TRUNCATED AT 400 WORDS)
在反刍动物的排卵前卵泡中已检测到催产素（OT）。牛颗粒细胞表达催产素/神经垂体素I（OT/NP-I）基因，并在体外分泌OT。本研究的目的是确定牛卵泡细胞在卵泡期分化以及排卵前卵泡接近排卵时OT分泌的发育模式。在黄体中期给荷斯坦小母牛注射前列腺素F2α以诱导黄体退化并启动卵泡期。在卵泡期早期、卵泡期中期或卵泡期晚期LH/FSH峰出现后，通过卵巢切除术获取含有排卵前卵泡的卵巢（每组4头小母牛）。分离卵泡内膜细胞和颗粒细胞，并在限定培养基或含血清培养基中单独或共培养5天，添加或不添加LH（300 ng/ml）或FSH（300 ng/ml）。每24小时收集并完全更换培养基，通过放射免疫分析法测定培养基中分泌的OT。在卵泡期的所有三个时间点分离的颗粒细胞均分泌可测量量的OT。然而，LH/FSH峰出现后分离的颗粒细胞的总OT分泌量比卵泡期早期分离的颗粒细胞的OT分泌量高18.9倍（限定培养基）至64.8倍（含血清培养基），比卵泡期中期分离的颗粒细胞的OT分泌量高14.6倍（限定培养基）至170倍（含血清培养基）。在LH/FSH峰出现前分离的颗粒细胞，培养基中添加LH或FSH会使其OT分泌增加。在LH峰出现前分离的颗粒细胞与卵泡内膜细胞的共培养物比单独的颗粒细胞培养物分泌更多的OT。当在卵泡期早期分离细胞时，共培养的效果大于相加作用，但当在卵泡期中期获取卵泡时，共培养的效果仅为相加作用。LH/FSH峰出现后分离的颗粒细胞的OT分泌不受促性腺激素或与卵泡内膜细胞共培养的影响。与颗粒细胞的结果相反，卵泡内膜细胞仅分泌少量且变化不定的OT，对LH的反应不一致。这些发现表明，在卵泡内膜细胞培养物中检测到的OT可能是由污染卵泡内膜细胞制剂的少量且数量不定的颗粒细胞产生的。（摘要截短至400字）
