Immunohistochemical evidence identifying the site of androgen production in the ovary of the protogynous grouper Epinephelus merra

Abstract

Androgen plays an important role in the developing ovaries of female fish. However, little is known regarding either the sites of production of androgen or its functional roles. In the present study, we investigated immunohistochemically the localization of cholesterol-side-chain-cleavage (P450scc) and cytochrome P45011beta-hydroxylase (P45011beta) with antibodies P450scc and P45011beta in the ovary of the female honeycomb grouper Epinephelus merra during its reproductive cycle. Clusters of strongly immunopositive cells, with 100-1000 cells in each cluster, against both P450scc and P45011beta, were observed throughout the annual reproductive cycle in tissue near blood vessels in the tunica ovary surrounding the outer periphery of the ovary. The ultrastructural characteristics of these cells showed that they were steroid-producing cells. In contrast, immunopositive cells against P450scc but not against P45011beta were localized in the theca layer surrounding the outer periphery of oocytes. These results suggest that two distinct steroid biosynthesis sites exist in the ovary and that cells at the two sites differ functionally. The only cells that biosynthesize 11-ketotestosterone are found in clusters in the vicinity of blood vessels; they possibly play a physiological role in oocyte growth and gonadal restructuring during the sex change of individuals of this species.

Examination of the Ability of Gonadal Sex Change in Primary Males of the Diandric Wrasses Halichoeres poecilopterus and Halichoeres tenuispinis: Estrogen Implantation Experiments

“…Together with histological observation, these results further strengthen our conclusion that the function of FSH is to induce gonadal sex change and spermatogenesis by stimulating androgen production. Previously, we observed that cell clusters immunostained with antibodies to P450 11b-hydoroxylase, which is the key steroidogenic enzyme for production of 11KT, were localized around blood vessels in the tunica albuginea of the ovary [59]. Based on this observation and data from the present study, we hypothesize that FSH acts on these cell clusters at the beginning of the sex change process to stimulate 11KT production.…”

Identification and Transcriptional Modulation of the Largemouth Bass, Micropterus salmoides, Vitellogenin Receptor During Oocyte Development by Insulin and Sex Steroids1

“…Recently, clusters of steroid-producing cells in the tunica of fish ovary have been detected as the site for biosynthesis of 11-KT [64] in support of this possibility. In addition, crosstalk between the AR and ER pathways has been suggested, through soluble and membrane receptors as a mechanism for dual involvement of both steroids.…”

Molecular mechanisms underlying sex change in hermaphroditic groupers

“…In many sexchanging fish, the levels of circulating 11-KT have been reported to increase with the progression of sex change (Nakamura et al 1989;Johnson et al 1998;Kroon and Liley 2000;Bhandari et al 2003), and exogenous 11-KT treatment can induce sex reversal (Kroon and Liley 2000;Yeh et al 2003). It was found that the androgen-producing sites exist in the ovary of honeycomb grouper (Alam et al 2005) and that naturally occurring sex change is accompanied by significant increases in the size of androgen-producing cells and production of androgen by the gonads . The data suggest that androgens play an important role in fish sex change.…”