Magoffin D A, Weitsman S R
Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center/University of California School of Medicine, Los Angeles 90048.
Endocrinology. 1993 May;132(5):1945-51. doi: 10.1210/endo.132.5.8477646.
Insulin-like growth factor-I (IGF-I) has been shown to synergistically augment LH-stimulated androgen biosynthesis in ovarian theca-interstitial cells (TIC). Additional evidence suggests that IGF-I may play a role in stimulating TIC differentiation during early follicle development. The purpose of the present studies was to examine the role of IGF-I in TIC differentiation by determining the effects of IGF-I on P450(17 alpha) mRNA expression in TIC differentiating in vitro. TIC isolated from the ovaries of hypophysectomized immature rats by Percoll gradient centrifugation were cultured with and without LH and IGF-I for up to 6 days. At various times, cytoplasmic RNA was extracted from the TIC, and P450(17 alpha) mRNA was measured by a specific assay, using reverse transcription and the polymerase chain reaction. LH stimulated a dose-related increase in P450(17 alpha) mRNA, with an ED50 comparable to that for androsterone biosynthesis (33.0 +/- 3.8 ng/ml), but significantly less than the ED50 for cAMP accumulation (385 +/- 0.1 ng/ml). IGF-I alone did not stimulate P450(17 alpha) mRNA, but in the presence of LH (100 ng/ml) stimulated a dose-related (ED50, 4.1 +/- 1.6 ng/ml) increase (3-fold) in P450(17 alpha) mRNA. IGF-I did not alter the ED50 for LH stimulation of P450(17 alpha) mRNA (36.85 +/- 1.1 ng/ml). Detailed time-course studies revealed that IGF-I did not alter the 20-h lag phase before LH caused an increase in TIC androsterone biosynthesis; however, IGF-I stimulated a more rapid increase in androsterone than LH alone. In the presence of LH alone, P450(17 alpha) mRNA levels remained low for approximately 18 h, then increased rapidly to maximum levels by 30 h where they were maintained through 48 h. Concomitant treatment with LH plus IGF-I did not alter the 18-h lag phase, but P450(17 alpha) mRNA levels increased to approximately 2-fold higher levels than with LH alone. The results of our studies demonstrate that IGF-I increases the expression of P450(17 alpha) mRNA in TIC and support the hypothesis that IGF-I may play a role in stimulating thecal differentiation in developing follicles.
胰岛素样生长因子-I（IGF-I）已被证明可协同增强促黄体生成素（LH）刺激的卵巢卵泡膜间质细胞（TIC）雄激素生物合成。更多证据表明，IGF-I可能在卵泡早期发育过程中刺激TIC分化方面发挥作用。本研究的目的是通过确定IGF-I对体外分化的TIC中P450（17α）mRNA表达的影响，来研究IGF-I在TIC分化中的作用。通过Percoll梯度离心从垂体切除的未成熟大鼠卵巢中分离出的TIC，在有或无LH和IGF-I的情况下培养长达6天。在不同时间，从TIC中提取细胞质RNA，并使用逆转录和聚合酶链反应通过特异性测定法测量P450（17α）mRNA。LH刺激P450（17α）mRNA呈剂量相关增加，其半数有效剂量（ED50）与雄甾酮生物合成的ED50相当（33.0±3.8 ng/ml），但明显低于cAMP积累的ED50（385±0.1 ng/ml）。单独的IGF-I不刺激P450（17α）mRNA，但在存在LH（100 ng/ml）的情况下刺激P450（17α）mRNA呈剂量相关（ED50，4.1±1.6 ng/ml）增加（3倍）。IGF-I不改变LH刺激P450（17α）mRNA的ED50（36.85±1.1 ng/ml）。详细的时间进程研究表明，IGF-I不改变LH导致TIC雄甾酮生物合成增加之前的20小时延迟期；然而，IGF-I比单独的LH刺激雄甾酮增加得更快。在仅存在LH的情况下，P450（17α）mRNA水平在大约18小时内保持较低，然后在30小时迅速增加到最高水平，并在48小时内维持该水平。LH加IGF-I的联合处理不改变18小时的延迟期，但P450（17α）mRNA水平比单独使用LH时增加到大约高2倍的水平。我们的研究结果表明，IGF-I增加TIC中P450（17α）mRNA的表达，并支持IGF-I可能在刺激发育卵泡中的卵泡膜分化中发挥作用的假设。
