Mechanism of angiotensin Ⅱ in regulation of renin synthesis in juxtaglomerular granular cells / 中华肾脏病杂志

ABSTRACT

Objective To elucidate the mechanism of angiotensin (Ang) Ⅱ in regulation of renin synthesis and secretion in primary cultured juxtaglomerular granular cells (JGCs). Methods Mice JGCs were isolated and cultured as described before. Real-time PCR was used to demonstrate the expression of angiotensin converting enzyme (CE) and angiotencin receptor (AT1, AT2) in JGCs. Ang Ⅱ was co-cultured with JGCs stimulated by PGE2 and isoproternol or not. Renin activity in supernatant was detected by radioimmunoassay and renin mRNA expression was examined by real-time PCR. Different concentrations of Ang Ⅱ were co-cultured with JGCs with different time (1 h, 4 h and 24 h), cAMP in cell lysate and supernatant was measured by Cayman Cyclic AMP EIA Kit. The cytoplasmic calcium was decreased by BAPTA-AM, and increased by thapsigargin and cyclopiazonic acid, which could be used to observe the cAMP concentration affected by calcium. Adenylyl cyclase type 5, 6 (AC5, AC6) mRNA expression of JGCs co-cultured with Ang Ⅱ was measured by real-time PCR. Results Real-time PCR confirmed the expression of ACE and AT mRNA in JGCs of WT mice. Angiotensin Ⅱ reduced renin secretion in primary cultures of JGCs [(370.6±36.9) vs (299.6±25.7) ng AngI'ml~(-1)·h~(-1), P=0.014]. Angiotensin Ⅱ dose-dependently down-regulated forskolin-stimulated cAMP production in JGCs. Thapsigargin and cyclopiazonic acid decreased cAMP level. BAPTA-AM increased cAMP production obviously [(11.09±0.48) vs (3.55±0.47) nmol/L, P<0.01]. Ang Ⅱ inhibited AC5 mRNA expression by 42.12%, but did not inhibit AC6 mRNA expression. Conclusions Angiotensin Ⅱ can directly inhibit renin synthesis and secrestion maybe through reducing AC-stimulated cAMP levels. Crosstalk between calcium and cAMP system may exist in precise regulation of renin in JGCs.