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Murata R.,University of Ryukyus | Kobayashi Y.,University of Ryukyus | Kobayashi Y.,Okinawa Institute of Advanced Science | Kobayashi Y.,Okayama University | And 5 more authors.
General and Comparative Endocrinology | Year: 2012

The aim of this study was to clarify the roles of 2 gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), on sex differentiation in the protogynous Malabar grouper, Epinephelus malabaricus. To do this, the mRNA expression patterns of GTH subunits (cga, fshb, and lhb) in the fish pituitary throughout gonadal sex differentiation were investigated. Real-time reverse transcriptase (RT)-PCR showed that cga and fshb were present in the undifferentiated and ovarian differentiation stages, and that the expression levels significantly increased after ovarian differentiation (AOD). However, lhb was not expressed before ovarian differentiation (BOD) and was first detected AOD. Next, to investigate the differentiation and distribution of Fshb and Lhb-producing cells in the pituitary of fish throughout gonadal sex differentiation, immunohistochemical analysis was used to detect teleost GTH subunits. Positive immunoreactivity against Fshb and Lhb was not detected in the pituitary BOD; Fshb and Lhb-positive cells first appeared in the pituitary AOD. It therefore seems unlikely that pituitary gonadotropins play a major role in the control of gonadal sex differentiation in the Malabar grouper. © 2012 Elsevier Inc..

Murata R.,University of Ryukyus | Karimata H.,Forestry and Fisheries | Kobayashi Y.,University of Ryukyus | Horiguchi R.,Japan National Institute for Basic Biology | And 6 more authors.
International Journal of Developmental Biology | Year: 2011

To understand the mechanism of sex differentiation in the protogynous Malabar grouper Epinephelus malabaricus, we performed an immunohistochemical investigation of the expression of three steroidogenic enzymes, cholesterol-side-chain-cleavage enzyme (CYP11a), aromatase (CYP19a1a), and cytochrome P45011beta-hydroxylase (CYP11b), in the gonads during ovarian differentiation. Strong positive immunoreactivity against CYP11a, the key enzyme of steroidogenesis, and CYP19a1a which is essential for estrogen (17beta-estradiol) production, appeared first in the somatic cells surrounding gonial germ cells in undifferentiated gonads and throughout ovarian differentiation. However, positive immunoreactivity against CYP11b, which is important for androgen (11-ketotestosterone) production, first appeared in the cluster of somatic cells in the ovary tunica near the dorsal blood vessel after differentiation. CYP19a1a and CYP11b did not co-localize in any cells. These results indicate that there are two types of steroid-producing cells, estrogen-producing cells and androgen-producing cells, in the gonads of this fish, and they are distributed differently, suggesting that these cells are derived from different somatic cells. Estrogen-producing cells appeared prior to ovarian differentiation, while androgen-producing cells were first detected after ovarian differentiation. These results suggest that endogenous estrogen is involved in ovarian differentiation. © 2011 UBC Press.

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