Intraovarian immunolocalization of steroidogenic enzymes in a Hokkaido brown bear, Ursus arctos yesoensis during the mating season

Publication Type:Journal Article
Year of Publication:1996
Authors:Araki, H, Tsubota, T, Kita, I, Maeda, N, Harada, N, Kominami, S, Mason, JI
Journal:Journal of Veterinary Medical Science
Volume:58
Pagination:787-790
Date Published:1996
Keywords:Ursus arctos
Abstract:

Immunolocalization for four steroidogenic enzymes was performed on an ovary taken from a Hokkaido brown bear during the mating season. This specimen is considered to be in the follicular phase because of the presence of large follicles. In large follicles, cholesterol side-chain cleavage (P450scc) and 3?-hydroxysteroid dehydrogenase (3?HSD) were immunolocalized in theca interna cells and granulosa cells. 17?-hydroxylase/C17-C20 lyase cytochrome P450 (P450c 17) was immunolocalized in theca interna cells but not in granulosa cells. Aromatase cytochrome P450 (P450arom) was immunolocalized only in granulosa cells. In medium follicles, however, P450scc and 3?HSD were immunolocalized only in theca interna cells, and the immunoreactivity of P450arom was detected in neither theca interna cells nor granulosa cells. Immunoreactivities of P450scc, 3?HSD and P450c17 but not P450arom were detected in interstitial cells. This study suggests that estrogen biosynthesis takes place through interrelation between theca cells and granulosa cells and is explained by the so-called two-cell mechanism. Furthermore, the granulosa cells in large follicles have the capability for pregnenolone and progesterone biosynthesis, and the interstitial cell in the bear ovary is also a steroidogenic site.

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