Tischkau S A, Neitzel L R, Walsh J A, Bahr J M
Department of Animal Sciences, University of Illinois at Urbana-Champaign, 61801, USA.
Biol Reprod. 1997 Feb;56(2):469-74. doi: 10.1095/biolreprod56.2.469.
Anatomical studies have suggested that the germinal disc (GD) region (GDR; GD plus overlying granulosa cells) is the growth center of the avian preovulatory follicle. The objective of this study was to characterize the physiology of the GDR by comparing the functions of two morphologically distinct populations of granulosa cells. The three markers of the physiology of individual granulosa cells examined were 1) proliferation, 2) production of plasminogen activator (PA), and 3) production of progesterone. The effect of LH on each of these functions was also evaluated. Sections 8 mm in diameter were obtained from granulosa cells associated with the GD (GD granulosa cells) and from granulosa cells on the layer distal to the GD (nonGD granulosa cells) from the five largest preovulatory follicles (F5-F1, F1 designated the largest) 12-14 h (before the LH surge) or 2 h (after the LH surge) before ovulation. Proliferation was measured using [3H]thymidine incorporation. PA activity was measured using the chromogenic substrate S-2251. Progesterone was measured by RIA. Incorporation of [3H]thymidine was very high in GD and nonGD granulosa cells from F5 and F4 follicles and decreased dramatically as the follicle progressed through the hierarchy, but remained significantly higher in GD granulosa cells compared to nonGD granulosa cells at all stages of development examined (F5-F1). Exposure of follicles to LH in vivo inhibited [3H]thymidine incorporation by GD granulosa cells in all follicles except the F5. In contrast, in vivo exposure to LH had no effect on [3H]thymidine incorporation by nonGD granulosa cells. PA production by GD granulosa cells was high throughout the stages of maturation studied (F5-F1), whereas PA production by nonGD granulosa cells decreased as follicles matured from F5 to F1. Interestingly, LH stimulated PA production by F5 GD granulosa cells, had no effect on PA production by F3 GD granulosa cells, and inhibited PA production by F1 GD granulosa cells. In contrast, LH inhibited PA production by nonGD granulosa cells in F3 and F1 follicles. Progesterone production by GD granulosa cells was low in F3 and F1 follicles. Progesterone production by nonGD granulosa cells increased as the follicle matured from the F3 to F1 stage and was stimulated significantly by LH. These data indicate that physiological differences in granulosa cell function are dependent upon the location of granulosa cells relative to the GD. GD granulosa cells are less mature, proliferate more rapidly, and produce more PA than nonGD granulosa cells, which produce more progesterone and less PA. Differences in granulosa cell function may be due to the influence of the GD, providing physiological evidence that the GDR may be the growth center of the follicle.
解剖学研究表明，胚盘（GD）区域（GDR；GD加上覆盖的颗粒细胞）是禽类排卵前卵泡的生长中心。本研究的目的是通过比较两种形态上不同的颗粒细胞群体的功能来表征GDR的生理学特性。所检测的单个颗粒细胞生理学的三个标志物为：1）增殖，2）纤溶酶原激活物（PA）的产生，3）孕酮的产生。还评估了促黄体生成素（LH）对这些功能中每一项的影响。从五个最大的排卵前卵泡（F5 - F1，F1为最大卵泡）排卵前12 - 14小时（LH峰前）或2小时（LH峰后）获取直径8毫米的切片，这些切片来自与GD相关的颗粒细胞（GD颗粒细胞）以及GD远端层的颗粒细胞（非GD颗粒细胞）。使用[³H]胸腺嘧啶核苷掺入法测量增殖。使用发色底物S - 2251测量PA活性。通过放射免疫分析法测量孕酮。[³H]胸腺嘧啶核苷掺入在F⁵和F⁴卵泡的GD和非GD颗粒细胞中非常高，并且随着卵泡在等级结构中进展而显著降低，但在所有检查的发育阶段（F5 - F1），GD颗粒细胞中的掺入量仍显著高于非GD颗粒细胞。卵泡在体内暴露于LH抑制了除F5外所有卵泡中GD颗粒细胞的[³H]胸腺嘧啶核苷掺入。相反，体内暴露于LH对非GD颗粒细胞的[³H]胸腺嘧啶核苷掺入没有影响。在整个研究的成熟阶段（F5 - F1），GD颗粒细胞的PA产生量都很高，而随着卵泡从F5成熟到F1，非GD颗粒细胞的PA产生量下降。有趣的是，LH刺激F5 GD颗粒细胞的PA产生，对F3 GD颗粒细胞的PA产生没有影响，并抑制F1 GD颗粒细胞的PA产生。相反地，LH抑制F3和F1卵泡中非GD颗粒细胞的PA产生。F3和F1卵泡中GD颗粒细胞的孕酮产生量较低。随着卵泡从F3成熟到F1阶段，非GD颗粒细胞的孕酮产生量增加，并且受到LH的显著刺激。这些数据表明，颗粒细胞功能的生理差异取决于颗粒细胞相对于GD的位置。GD颗粒细胞比非GD颗粒细胞更不成熟，增殖更快，产生更多的PA，而非GD颗粒细胞产生更多的孕酮且产生较少的PA。颗粒细胞功能的差异可能是由于GD的影响，为GDR可能是卵泡的生长中心提供了生理学证据。
