Haider S, Chaube S K
Department of Zoology, Banaras Hindu University, Varanasi, India.
Comp Biochem Physiol C Pharmacol Toxicol Endocrinol. 1996 Oct;115(2):117-23. doi: 10.1016/s0742-8413(96)00050-3.
The effects of an adenylate cyclase activator (forskolin, FK), phosphodiesterase inhibitor (3-isobutyl-l-methyl-xanthine, IBMX) and an inhibitor of steroidogenesis (cyanoketone, CK) on germinal vesicle breakdown (GVBD) in the catfish (Clarias batrachus) were investigated in vitro. In most of the experiments GVBD was induced by using 1 microgram/ml 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-DP), which is the maturation-inducing steroid (MIS) for this species. Adenosine 3':5'-cyclic monophosphate (cAMP) levels were also measured in the control, MIS-induced and/or FK- and IBMX-treated follicle-enclosed oocytes. MIS-induced GVBD was inhibited by FK (> or = 0.5 microM) or IBMX (> or = 1.0 mM), but oocyte exposed to 0.1 microM FK or 0.5 mM IBMX, after MIS stimulation, underwent GVBD. However, an inhibition of GVBD was recorded when the MIS-induced folliculated oocytes were preincubated with CK (1 microgram/ml) and subsequently treated with 0.1 microM FK. In the time course study, when the oocytes were stimulated by MIS for various time intervals and then treated with 1.0 microM FK or 1.0 mM IBMX, both the substances blocked maturation if they were added up to 12 hr after MIS. The extent of inhibition was gradually decreased and was completely removed after 30 hr of post-MIS stimulation. The stimulatory dose of 17 alpha,20 beta-DP (1 microgram/ml) not only induced GVBD (83.2 +/- 1.50%) in vitro but also reduced oocyte cAMP level (65.3 +/- 2.85 pmol/100 micrograms protein) significantly after 6 hr of incubation. However, FK (10.0 microM) or IBMX (1.0 mM) countered these effects and promoted the accumulation of cAMP in the oocytes; FK being more potent. On the other hand, when unstimulated full-grown but immature oocytes were cultured in vitro in the presence of different concentrations of FK, an induction of oocyte maturation was recorded in dose- and time-dependent manner. These results strongly suggest the involvement of cAMP in the regulation of catfish oocyte maturation.
体外研究了腺苷酸环化酶激活剂（福斯高林，FK）、磷酸二酯酶抑制剂（3-异丁基-1-甲基黄嘌呤，IBMX）和类固醇生成抑制剂（氰酮，CK）对鲶鱼（胡子鲶）生发泡破裂（GVBD）的影响。在大多数实验中，使用1微克/毫升的17α,20β-二羟基-4-孕烯-3-酮（17α,20β-DP）诱导GVBD，17α,20β-DP是该物种的成熟诱导类固醇（MIS）。还在对照、MIS诱导和/或FK和IBMX处理的卵泡包被卵母细胞中测量了3':5'-环磷酸腺苷（cAMP）水平。MIS诱导的GVBD被FK（≥0.5微摩尔）或IBMX（≥1.0毫摩尔）抑制，但在MIS刺激后暴露于0.1微摩尔FK或0.5毫摩尔IBMX的卵母细胞发生了GVBD。然而，当MIS诱导的卵泡卵母细胞预先用CK（1微克/毫升）孵育，随后用0.1微摩尔FK处理时，记录到GVBD受到抑制。在时间进程研究中，当卵母细胞用MIS刺激不同时间间隔，然后用1.0微摩尔FK或1.0毫摩尔IBMX处理时，如果在MIS后12小时内添加这两种物质，它们都会阻断成熟。抑制程度逐渐降低，在MIS刺激后30小时完全消除。17α,20β-DP（1微克/毫升）的刺激剂量不仅在体外诱导了GVBD（83.2±1.50%），而且在孵育6小时后显著降低了卵母细胞cAMP水平（65.3±2.85皮摩尔/100微克蛋白质）。然而，FK（10.0微摩尔）或IBMX（1.0毫摩尔）抵消了这些影响，并促进了卵母细胞中cAMP的积累；FK更有效。另一方面，当未刺激的完全成熟但未成熟的卵母细胞在不同浓度的FK存在下进行体外培养时，以剂量和时间依赖性方式记录到卵母细胞成熟的诱导。这些结果强烈表明cAMP参与了鲶鱼卵母细胞成熟的调节。
