Stimulation of renin secretion by catecholamines is dependent on adenylyl cyclases 5 and 6

Abstract

The sympathetic nervous system stimulates renin release from juxtaglomerular cells via the β-adrenoreceptor-cAMP pathway. Recent in vitro studies have suggested that the calcium-inhibited adenylyl cyclases (ACs) 5 and 6 possess key roles in the control of renin exocytosis. To investigate the relative contribution of AC5 and AC6 to the regulation of renin release in vivo we performed experiments using AC5 and AC6 knockout mice. Male AC5(-/-) mice exhibited normal plasma renin concentrations, renal renin synthesis (mRNA and renin content), urinary volume, and systolic blood pressure. In male AC6(-/-) mice, plasma renin concentration (AC6(-/-): 732 ± 119; AC6 (+/+): 436 ± 78 ng of angiotensin I per hour*mL(-1); P<0.05), and renin synthesis were stimulated associated with an increased excretion of dilute urine (1.55-fold; P<0.05) and reduced blood pressure (-10.6 mm Hg; P<0.001). Stimulation of plasma renin concentration by a single injection of the β-adrenoreceptor agonist isoproterenol (10 mg/kg IP) was significantly attenuated in AC5(-/-) (male: -20%; female: -33%) compared with wild-type mice in vivo. The mitigation of the plasma renin concentration response to isoproterenol was even more pronounced in AC6(-/-) (male: -63%; female: -50% versus AC6(+/+)). Similarly, the effects of isoproterenol, prostaglandin E2, and pituitary adenylyl cyclase-activating polypeptide on renin release from isolated perfused kidneys were attenuated to a higher extent in AC6(-/-) (-51% to -98% versus AC6(+/+)) than in AC5(-/-) (-31% to 46% versus AC5(+/+)). In conclusion, both AC5 and AC6 are involved in the stimulation of renin secretion in vivo, and AC6 is the dominant isoforms in this process.

Figure 1

A: In situ hybridization using antisense mRNA probes specific for AC5 (left), AC6 (middle) and renin (right). Hybridization with sense mRNA probes did not produce staining. B: mRNA expression of AC5 (left) and AC6 (right) in single mouse JG cells. C: mRNA expression of AC isoforms in isolated JG cells of AC5 (left) and AC6 (right) knockout mice compared to their wildtypes (n=4 each genotype).

Figure 2

Baseline physiological characteristics of AC6 knockout (AC6 KO, black bars) and wildtype mice (AC6 WT, white bars). * p < 0.05 vs. AC6 WT; ** p < 0.01 vs. AC6 WT

Figure 3

Representative immunofluorescence staining for renin (green) in kidneys of AC5 wildtype (AC +/+), AC5 knockout (AC5 −/−), AC6 wildtype (AC6 +/+) and AC6 knockout (AC6 −/−) mice.

Figure 4

Mean increase of PRC over basal caused by isoproterenol (10mg / kg body weight) in AC5 (upper panel) and AC6 (lower panel) knockout mice. ** p < 0.001 vs. baseline PRC

Figure 5

Renin secretion rates of isolated perfused kidneys of AC5 knockout (A, C) or AC6 knockout (B, D) mice and their respective wildtypes. A and B: Effect of prostagandinE2 (PGE2) 10 nMol/L, PACAP 10nMol/L, the membrane permeable cAMP analogue 8bromo-cAMP 200μMol/L C and D: Effect of angiotensinII (angII) on renin secretion rates. In order to be able to detect inhibition of renin release, renin secretion rates are prestimulated by isoproterenol 10nMol/L and angII is applied in the presence of isoproterenol. * p < 0.05 vs. control + p < 0.05 wildtype vs. knockout

Figure 6

Mean increase in renin secretion rates over basal from isolated perfused kidneys of AC5 (upper panel) and AC6 wildtype knockout kidneys (lower panel). * p < 0.05 ** p < 0.001 vs. baseline renin secretion rate + p < 0.05 ++ p < 0.001 wildtype vs. knockout