In vivo regulation of steroidogenesis by ovine gonadotropins in male and female mudpuppies, Necturus maculosus Rafinesque

Abstract

Using steroid radioimmunoassay the in vivo steroidogenic responses of male and female mudpuppies ( Necturus maculosus) to single injections of ovine FSH and LH were investigated. In males, the major effect of LH was to stimulate testosterone and 5α-dihydrotestosterone secretion within 2 hr of injection, with a lesser effect on estrogen (estrone and estradiol-17β) secretion. In contrast, FSH primarily stimulated secretion of estrogens. The effects of both FSH and LH on steroid secretion in males were dose related. Castration of males reduced plasma androgen, and estrogen to very low or nondetectable levels and abolished the steroidogenic response to LH. Interrenalectomy prevented a postcastration rise in the progesterone level. In females, FSH did not stimulate steroid secretion but LH increased plasma androgens. Homologous pituitary extracts also stimulated plasma levels of all gonadal steroids measured.