Mechanisms of synthesis and action of 17α,20β-dihydroxy-4-pregnen-3-one,a teleost maturation-inducing substance |
| |
Authors: | Yoshitaka Nagahama Masakane Yamashita |
| |
Institution: | (1) Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444, Japan;(2) Present address: Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444, Japan |
| |
Abstract: | This article briefly reviews the current status of investigations, mainly based on the amago salmon,Oncorhynchus rhodurus, on the mechanisms of synthesis and action of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-diOHprog). Pituitary gonadotropin
is of primary importance in triggering meiotic maturation in teleost oocytes. However, the maturational action of gonadotropin
is not direct, but is mediated by the follicular production of maturation-inducing substance (MIS). It is now well established
that 17α,20β-diOHprog is the major MIS of salmonids. Production of this steroid occursvia the interaction of two distinct cell layers, the thecal and granulosa cell layers (2-cell type model). The first step of
the stimulating effect of gonadotropin in both layers is the receptor-mediated activation of adenylate cyclase and formation
of cAMP. Our findings suggest that the major stimulating action of gonadotropin on 17α,20β-diOHprog biosynthesis is due to
the stimulation of 17α-hydroxyprogesterone production by the thecal layer and the selective induction of thede novo synthesis of 20β-hydroxysteroid dehydrogenase in the granulosa layer. 17α,20β-diOHprog acts at the surface of the oocyte.
The early steps following 17α,20β-diOHprog action involve the formation of the major cytoplasmic mediator of this steroid,
maturation-promoting factor (MPF). It was shown that goldfish MPF induces meiotic maturation inXenopus oocytes andvice versa. The chemical characterization of fish MPF is important for our understanding of the precise mode of maturational action
of 17α,20β-diOHprog. |
| |
Keywords: | oocyte maturation gonadotropin maturation-inducing substance 17α 20β -dihydroxy-4-pregnen-3-one steroidogenesis ovarian follicles maturation-promoting factor |
本文献已被 SpringerLink 等数据库收录! |
|