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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-αMSH and ir-βEP (β-endorphin) were substantially and significantly raised in HPD compared with control plasma. Size exclusion HPLC showed plasma βEP/βLPH (β-lipotropin) levels to be higher in HPD than control ewes. Dexamethasone administration lowered plasma ir-ACTH but not ir-βEP; in contrast, bromocriptine lowered ir-βEP but not ir-ACTH. We interpret these data as evidence (1) that the elevated plasma levels of ir-βEP and ir-αMSH 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.

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 >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.In vitro models for studying renin biosynthesis and its regulation are needed because of the multiple factors that influence renin production and secretion in vivo. Such studies have been limited, however, by the difficulty in establishing juxtaglomerular cell (JGC) cultures, which is due primarily to the scarcity of these cells in the kidney. Primary cultures of renin-secreting cells have been described recently in the rat by Kurtz et al. (1) and in the human in two cases of JGC tumors (2, 3). Galen et al. (3) cultured renin-secreting tumor cells for >1 month in both primary and secondary cultures. Renin was synthesized as an inactive precursor that had all of the biochemical and immunological characteristics of pure standard renin. The sole attempt to maintain a JGC culture has been made by Rightsel et al. (4) in the rat by subculturing and cloning dissociated cortical cells from neonatal kidney.Recent studies have shown that endocrine cells can be transformed by simian virus 40 (SV40) or SV40 mutants. This allows the establishment of cell lines that maintain their differentiated state. These differentiated cell lines are able to secrete choriogonadotropin (5) and insulin (6). We were encouraged to use a similar approach to establish reninproducing cell lines by transformation of human JGC with SV40 mutants. In the present study, continuous JGC lines, producing renin, were obtained and characterized by various morphologic techniques. METHODSPrimary Culture. The renin content of the JGC tumor used was 1128 Goldblatt units (GU)/g of tissue. More than 95% of this renin was in the active form. A 5-g fragment of this tumor was dissociated by enzymatic digestion as described by Galen et al. (3). Cells were plated at a density of 106 cells per 25-cm2 flask and ...

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