Masuda M, Kubota T, Aso T
Department of Obstetrics and Gynecology, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-0034, Japan.
Eur J Endocrinol. 2001 Mar;144(3):303-8. doi: 10.1530/eje.0.1440303.
We have previously demonstrated that nitric oxide (NO) inhibits steroidogenesis via a cGMP-independent process, by inhibiting P450 aromatase activity in porcine granulosa cells (PGCs) derived from medium-sized (3--5 mm) ovarian follicles (M-PGC).
To determine whether the NO/NO synthase (NOS) system exerts any significant effects on steroidogenesis in PGCs derived from small follicles (<3 mm) (S-PGC) in comparison with those derived from medium follicles.
PGCs, namely S-PGC and M-PGC, were incubated with the NO donor, NOC18, and a competitive blocker of NOS, N(3)-monomethyl-l-arginine (LNMMA), either alone or in the presence of FSH (200 ng/ml) or hCG (5 IU/ml).
NOC18 significantly (P<0.01--0.001) suppressed basal (unstimulated) and gonadotropin-stimulated estradiol (E2) release from both S-PGC and M-PGC in a 2-h culture. NOC18 significantly (P<0.01--0.001) decreased basal and gonadotropin-stimulated progesterone release from S-PGC, but not from M-PGC. In addition, NOC18 significantly (P<0.05--0.001) inhibited aromatase activity in S-PGC. LNMMA had a significantly (P<0.01--0.001) stimulatory effect on the basal release of E2 and progesterone from M-PGC; however, it had no significant effect on basal steroidogenesis in S-PGC in a 24-h culture. In the presence of gonadotropin, LNMMA significantly (P<0.01--0.001) stimulated the release of E2 and progesterone from both S- and M-PGC, and this stimulatory effect was weaker in S-PGC than in M-PGC. These results demonstrate that NO inhibits E2 secretion by directly inhibiting the aromatase activity in S-PGC, as in M-PGC. It has been shown that the NO system suppresses the differentiation of S-PGC; however, the extent of suppression decreased with the progression of follicular growth. In addition, the activity of NOS in S-PGC was weaker than that in M-PGC.
We strongly suggest that the NO/NOS system in PGC regulates steroidogenesis differently during different phase of follicular development.
我们之前已经证明，一氧化氮（NO）通过抑制源自中等大小（3 - 5 毫米）卵巢卵泡（M-PGC）的猪颗粒细胞（PGCs）中的 P450 芳香化酶活性，经由不依赖环磷酸鸟苷（cGMP）的过程抑制类固醇生成。
确定与源自中等卵泡的颗粒细胞相比，NO/一氧化氮合酶（NOS）系统对源自小卵泡（<3 毫米）的颗粒细胞（S-PGC）的类固醇生成是否有任何显著影响。
将颗粒细胞，即 S-PGC 和 M-PGC，单独或在促卵泡激素（FSH，200 纳克/毫升）或人绒毛膜促性腺激素（hCG，5 国际单位/毫升）存在的情况下，与 NO 供体 NOC18 和 NOS 的竞争性阻滞剂 N(3)-单甲基-L-精氨酸（LNMMA）一起孵育。
在 2 小时的培养中，NOC18 显著（P<0.01 - 0.001）抑制了 S-PGC 和 M-PGC 的基础（未刺激）和促性腺激素刺激的雌二醇（E2）释放。NOC18 显著（P<0.01 - 0.001）降低了 S-PGC 的基础和促性腺激素刺激的孕酮释放，但对 M-PGC 没有影响。此外，NOC18 显著（P<0.０5 - 0.001）抑制了 S-PGC 中的芳香化酶活性。LNMMA 对 M-PGC 的 E2 和孕酮基础释放有显著（P<０.０1 - 0.001）刺激作用；然而，在 24 小时培养中，它对 S-PGC 的基础类固醇生成没有显著影响。在存在促性腺激素的情况下，LNMMA 显著（P<０.０1 - 0.001）刺激了 S-PGC 和 M-PGC 中 E2 和孕酮的释放，并且这种刺激作用在 S-PGC 中比在 M-PGC 中更弱。这些结果表明，与 M-PGC 的情况一样，NO 通过直接抑制 S-PGC 中的芳香化酶活性来抑制 E2 分泌。已经表明，NO 系统抑制 S-PGC 的分化；然而，抑制程度随着卵泡生长的进展而降低。此外，S-PGC 中 NOS 的活性比 M-PGC 中的弱。
我们强烈建议，PGC 中的 NO/NOS 系统在卵泡发育的不同阶段对类固醇生成的调节方式不同。
