Dean C E, Byrd J A, Hargis B M
Department of Poultry Science, Texas Agricultural Experiment Station, Texas A&M University System College Station 77843, USA.
Domest Anim Endocrinol. 1995 Jan;12(1):51-61. doi: 10.1016/0739-7240(94)00007-n.
We have previously reported that a peptide from chicken bursa of Fabricius, bursal antisteroidogenic peptide (BASP), inhibits luteinizing hormone-stimulated progesterone biosynthesis by chicken ovarian granulosa cells. The objective of this study was to determine the site(s) of BASP inhibition within the steroidogenic pathway of chicken granulosa cells. The effects of BASP on key steroidogenic enzymes, including adenylyl cyclase (AC), phosphodiesterase, the cholesterol side-chain cleavage enzyme complex and 3 beta-hydroxysteroid dehydrogenase were determined. Luteinizing hormone (10 ng/tube) stimulated a fivefold increase in granulosa cell progesterone production that was inhibited by BASP (0.06, 0.12 or 0.25 bursal equivalents) in a dose-dependent manner. Luteinizing hormone stimulated a sixfold increase in cyclic 3',5'-adenosine monophosphate (cAMP) formation, and this increase was potentiated by BASP in a dose-dependent manner. In addition, BASP stimulated cAMP formation in the absence of luteinizing hormone without affecting progesterone production. The AC activator forskolin (0.1 mM) stimulated a 4.5-fold increase in progesterone synthesis, which was inhibited by BASP. In the presence of forskolin. BASP increased cAMP formation in a dose-dependent manner. A fivefold increase in progesterone synthesis induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) was inhibited by BASP. In the presence of 3-isobutyl-1-methylxanthine, BASP increased cAMP formation in a dose-dependent manner. Finally, 22(R)-hydroxycholesterol (250, 500, 1,000, or 2,500 ng/tube) or pregnenolone (50, 100, 200, or 500 ng/tube) resulted in up to 15- or 10-fold increases in progesterone production, respectively. Increasing concentrations of BASP caused a dose-dependent suppression of the conversion of 22(R)-hydroxycholesterol, but not pregnenolone, to progesterone. The inhibition of steroidogenesis by BASP is not associated with reduced cAMP levels, and BASP appears to strongly stimulate AC activity. In addition, these findings suggest that BASP may limit the availability of progesterone precursors by inhibiting the activity of the cholesterol side-chain cleavage enzyme complex.
我们之前曾报道，来自鸡法氏囊的一种肽——法氏囊抗类固醇生成肽（BASP），可抑制鸡卵巢颗粒细胞中促黄体生成素刺激的孕酮生物合成。本研究的目的是确定BASP在鸡颗粒细胞类固醇生成途径中的抑制位点。测定了BASP对关键类固醇生成酶的影响，包括腺苷酸环化酶（AC）、磷酸二酯酶、胆固醇侧链裂解酶复合物和3β-羟基类固醇脱氢酶。促黄体生成素（10 ng/管）刺激颗粒细胞孕酮生成增加了五倍，而BASP（0.06、0.12或0.25个法氏囊当量）以剂量依赖的方式抑制了这种增加。促黄体生成素刺激环磷酸腺苷（cAMP）形成增加了六倍，而BASP以剂量依赖的方式增强了这种增加。此外，BASP在没有促黄体生成素的情况下刺激了cAMP的形成，而不影响孕酮的生成。AC激活剂福斯可林（0.1 mM）刺激孕酮合成增加了4.5倍，这被BASP抑制。在福斯可林存在的情况下，BASP以剂量依赖的方式增加了cAMP的形成。磷酸二酯酶抑制剂3-异丁基-1-甲基黄嘌呤（1.0 mM）诱导的孕酮合成增加了五倍，被BASP抑制。在3-异丁基-1-甲基黄嘌呤存在的情况下，BASP以剂量依赖的方式增加了cAMP的形成。最后，22（R）-羟基胆固醇（250、500、1000或2500 ng/管）或孕烯醇酮（50、100、200或500 ng/管）分别导致孕酮生成增加高达15倍或10倍。BASP浓度增加导致22（R）-羟基胆固醇向孕酮的转化呈剂量依赖性抑制，但对孕烯醇酮向孕酮的转化无影响。BASP对类固醇生成的抑制与cAMP水平降低无关，且BASP似乎强烈刺激AC活性。此外，这些发现表明BASP可能通过抑制胆固醇侧链裂解酶复合物的活性来限制孕酮前体的可用性。
