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)

译文

在反刍动物排卵前卵泡中检测到催产素 (OT)。牛颗粒细胞在体外表达催产素/神经物理素I (OT/np-i) 基因并分泌OT。这项研究的目的是确定牛卵泡细胞在卵泡期和排卵前卵泡接近排卵时分化的OT分泌发育模式。荷斯坦小母牛在黄体中期注射前列腺素f2α,以诱导黄体消退并开始卵泡期。LH/FSH激增后,通过卵泡期早期,卵泡期中期或卵泡期晚期的卵巢切除术获得了带有排卵前卵泡的卵巢 (每组n = 4个小母牛)。分离卵泡膜和颗粒细胞,单独或在共培养中,在确定的或含血清的培养基中,在有或没有LH (300 ng/ml) 或FSH (300 ng/ml) 的情况下培养5天。每24小时收集并完全更换一次培养基,并用RIA测量分泌到培养基中的OT。在卵泡期的所有三个时间点分离出的颗粒细胞分泌了可测量的OT。然而,LH/FSH激增后分离的颗粒细胞的总OT分泌比卵泡期早期分离的颗粒细胞的OT分泌高18.9倍 (定义培养基) 至64.8倍 (含血清培养基),与卵泡中期分离的颗粒细胞的OT分泌相比,高14.6倍 (定义培养基) 至170倍 (含血清培养基)。在LH/FSH激增之前分离的颗粒细胞对向培养基中添加LH或FSH做出反应,从而增加了OT分泌。在LH激增之前分离的颗粒细胞和卵泡膜的共培养比单独的颗粒细胞培养分泌更多的OT。当在卵泡期早期分离细胞时,共培养的作用大于加性,但是当在卵泡期中期获得卵泡时,共培养的作用仅是加性的。LH/FSH激增后分离的颗粒细胞的OT分泌不受促性腺激素或与卵泡膜共培养的影响。与颗粒细胞的结果相反,卵泡膜仅分泌少量且可变量的OT,并且对LH的反应不一致。这些发现表明,在卵泡膜内部培养物中检测到的OT可能是由少量和可变数量的颗粒细胞污染卵泡膜内部制备物产生的。(摘要截短于400字)

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