OPPOSITE REGULATION OF RENIN GENE-EXPRESSION BY CYCLIC-AMP AND CALCIUM IN ISOLATED MOUSE JUXTAGLOMERULAR CELLS

A quantitative reverse transcriptase-polymerase chain reaction for mou se renin mRNA was utilized to study the influence of classic second me ssenger molecules on renin mRNA levels in primary cultures of juxtaglo merular (JG) cells isolated from the kidneys of C57/B16 mice. We found that forskolin (3 mu M), an activator of adenylate cyclase led to pro portional increases of renin secretion and renin mRNA levels. The nitr ic oxide (NO) donor, sodium nitroprusside (100 mu M), stimulated both renin secretion and renin gene expression, the effect on secretion bei ng stronger than that on renin mRNA levels. An increase of the extrace llular concentration of calcium from 0.5 to 3 mM led to a transient in hibition of renin secretion, followed by a marked stimulation of secre tion and to a continuous suppression of renin mRNA levels. These were also decreased by the calcium ionophore A23187 (1 mu M) The membrane p ermeable 8-bromo-cyclic GMP (100 mu M) inhibited basal renin secretion without an effect on renin mRNA levels. The phorbol ester phorbol-12- myristate-13-acetate (1 to 100 nM), which was used to stimulate protei n kinase C activity, had no significant effects on renin secretion and renin mRNA levels, neither alone nor in combination with forskolin. T hese findings suggest that cAMP, NO and calcium are effective regulato rs of renin gene expression in renal JG cells, in a way that cAMP and NO are stimulators and calcium acts as an inhibitor. Moreover, in thes e acute experiments there appears to be no obligatory link between the secretion and the expression of renin, suggesting that both parameter s are separately regulated.