Inhibin A-subunit gene expression in the ovaries of immature female rats is stimulated by pregnant mare serum gonadotrophin.

We have used a bovine cDNA probe for the A-subunit of inhibin to demonstrate the presence of inhibin in the ovaries of immature female rats: the levels of mRNA were increased following treatment of the rats with pregnant mare serum gonadotrophin (PMSG), suggesting modulation by PMSG of ovarian inhibin synthesis at least at the level of transcription. Furthermore, we report the unexpected finding of significant levels of inhibin mRNA in the corpora lutea of mature female rats. No inhibin mRNA was demonstrable in the uterus or placenta.

Elevated plasma levels of pro-opiomelanocortin-derived peptides in sheep following hypothalamo-pituitary disconnection.

We have studied the control of the pituitary-adrenal axis in ovariectomized sheep following hypothalamo-pituitary disconnection (HPD) by following plasma levels of immunoreactive (ir-) products of pro-opiomelanocortin (POMC). In ovariectomized HPD ewes, gonadotropin levels were below detection limits. In contrast, levels of ir-ACTH were modestly but significantly elevated over those in matched ovariectomized control ewes, though cortisol levels were not significantly different; levels of ir-alpha MSH and ir-beta EP (beta-endorphin) were substantially and significantly raised in HPD compared with control plasma. Size exclusion HPLC showed plasma beta EP/beta LPH (beta-lipotropin) levels to be higher in HPD than control ewes. Dexamethasone administration lowered plasma ir-ACTH but not ir-beta EP; in contrast, bromocriptine lowered ir-beta EP but not ir-ACTH. We interpret these data as evidence (1) that the elevated plasma levels of ir-beta EP and ir-alpha MSH post-HPD reflect the release of the intermediate lobe from tonic inhibitory dopaminergic control and (2) that, unlike the gonadotrope, hypothalamic releasing factors are not required for the maintenance of the corticotrope, or for baseline secretion of ACTH from these cells.

Isolation of renin-producing human cells by transfection with three simian virus 40 mutants.

A human juxtaglomerular cell (JGC) tumor was used for the immortalization of renin-secreting cells. The transfection of primary JGC with three different simian virus 40 (SV40) mutants resulted in the continuous production of renin-secreting cells. The most efficient renin-producing cells (producing about 400 pg of renin per 24 hr per ml of culture medium) were those transfected with the PAS SV40 mutant. The renin production was stable and the cell cultures have been maintained for greater than 1 year. Two types of cells were cultured together and could not be separated: round and birefringent cells, which exhibited features of mast cells, and elongated cells containing myofilaments and secretory granules. Immunocytochemical staining showed the presence of renin in this latter cell type. The renin produced by the transfected cells was not stored within the cells but was released rapidly into the medium. More than 95% of the renin produced was prorenin, which, after activation, had characteristics similar to those of pure human standard renin as to its enzymatic, immunologic, and biochemical properties, except that it was less glycosylated. These stable JGC tumoral cell lines provide a unique system for studying human renin biosynthesis and its regulation in vitro.