Regulation of prorenin secretion in cultured human transfected juxtaglomerular cells.

Abstract

The regulation of renin secretion was studied in continuous culture of human juxtaglomerular cells (JGC), which provided a permanent source of human renin production (Pinet, F., M. T. Corvol, F. Dench, J. Bourguignon, J. Feunteun, J. Menard, and P. Corvol, 1985, Proc. NatL Acad. Sci. USA,. 95% of the renin species secreted was prorenin, and therefore this study concerned primarily prorenin secretion. Renin production was stable, since the cells had been maintained in culture for more than two years. In culture, these human cells formed colonies of smooth musclelike cells, and electron microscopy showed the presence of cytoskeleton structures including myofibrils and attachment bodies. This human model was used to investigate the control of prorenin secretion in vitro at cellular level. Various pharmacological agents known to stimulate or inhibit renin secretion were tested in the cell cultures. The variations in prorenin secretion were measured in the supernatant. Forskolin, an independent receptor activator of adenylate cyclase, stimulated prorenin secretion in a dose-dependent manner and this stimulation was mediated by 3',5' cyclic-AMP (cAMP). Angiotensin II (All) was found to inhibit prorenin secretion directly in a dose-dependent manner and atrial natriuretic factor (ANF), whose effects on human JGC were characterized for the first time, was also shown to exert such inhibition. When the effects of this inhibition by All and ANF were tested on forskolin-mediated stimulation of prorenin secretion, the latter was inhibited and no change occurred in cAMP release. When JGC were treated with histamine, bradykinin, or one or two bradykinin analogues, the responses suggested that in these cells, H2-histamine receptors and kinin receptors are dependent on adenylate cyclase. One peptide, substance P., had an inhibitory effect on prorenin secretion but it was less important than All and ANF. The present results demonstrate that the adenylate cyclase system of human JGC remains intact during culture and supports the hypothesis that cAMP is the second messenger and Ca,2+ the final messenger involved in renin secretion. The cell system used here permits the evaluation of cellular responses and intracellular events in granulated cells in a human model.

Renin processing in cultured juxtaglomerular cells of the hydronephrotic mouse kidney.

“…This result suggests that, in culture, JG cells do not sort as much renin into the regulative pathway, thus allowing more pro-renin to accumulate in both proto-and intermediate granules. No evidence of exocytosis of pro-renin from proto- (29,37). Before exocytosis, mature granules in normal JG cells enlarge, become less electron dense, and fuse with each other and the plasma membrane (38,39).…”

“…Forskolin was added at concentrations of lo'* M, lo-> M, and 10" to fresh culture medium of Day 6 culture dishes for 8 hr, as it has been reported to stimulate renin release (3). Theophylline was also added at a concentration of lo4 M to the fresh culture medium containing forskolin, since it augments the level of intracellular CAMP above that obtained with forskolin alone (29). Theophylline alone has no significant effect on renin secretion from cultured JG cells (29).…”

“…Theophylline was also added at a concentration of lo4 M to the fresh culture medium containing forskolin, since it augments the level of intracellular CAMP above that obtained with forskolin alone (29). Theophylline alone has no significant effect on renin secretion from cultured JG cells (29). Verapamil, forskolin, and theophylline were obtained from Sigma.…”

Cellular control of renin secretion

“…Recently, the same group succeeded in transforming cultured tumoral juxtaglomerular cells by the use of SV40 virus infection (Pinet et al 1985). Although these cultures are not optimal for the study of exocytosis of renin they could be very valuable for the investigation of the control of renin and prorenin synthesis (Pinet et al 1987).…”

“…This hormone is the atrial natriuretic peptide (ANP) (Ballermann and Brenner 1985), and besides its natriuretic effect, it has also been found to inhibit renal renin release (Burnett et al 1984;Garcia et al 1985;Maack et al 1985). It was not clear whether ANP exerts its effect by a direct action on juxtaglomerular cells, or indirectly by activating the macula densa mechanism; therefore, the effects of ANP, on renin release from renal cortical slices (Obana et al 1985;Henrich et al 1986;Takagi et al 1988;Antonipillai et al 1986) and from rat (Kurtz et al 1986b) and tumoral human juxtaglomerular cells (Pinet et al 1987) were investigated. With the exception of one study (Tagaki et al 1986), the results revealed that ANP leads to a dose-dependent inhibition of renin release from these preparations.…”