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General Comment |
Wang YJ, et al 2002 reported the cloning of
20beta-Hydroxysteroid dehydrogenase. 20beta-HSD is a crucial enzyme that
converts 17alpha-hydroxyprogesterone to
17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP), which triggers oocyte
maturation in most teleost fish. A full-length cDNA for a carbonyl
reductase-like 20beta-HSD (CR/20beta-HSD) has been cloned from the zebrafish
ovary. Although the zebrafish CR/20beta-HSD is expressed in all of the tissues
tested, it is predominantly expressed in the ovary, testis, kidney, and gill.
In the ovary, the enzyme was shown to be expressed in the follicle cells and
its expression appeared to be constitutive. No significant difference was
noticed in the level of CR/20beta-HSD expression among follicles of different
stages. Furthermore, analysis of the ovarian samples taken at different times
before spawning showed no significant change of the enzyme expression. In
agreement with these results, treatment of the cultured zebrafish ovarian
follicle cells with gonadotropin and activin had little effect on the
expression of the enzyme. Taken together, these results point to the
possibility that the gonadotropin-induced DHP production and final oocyte
maturation in the zebrafish may not involve significant change of
CR/20beta-HSD expression as evidenced in the salmonids, or that there might be
other isoforms of 20beta-HSD whose expression is tightly controlled by
endocrine and paracrine factors.
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