Restoring nitric oxide cytosolic calcium regulation by cyclic GMP protein kinase Ialpha transfection in coronary endothelial cells of spontaneously hypertensive rats

ABSTRACT In microcoronary endothelial cells (RCEs) from spontaneously hypertensive rats (SHR), the NO/cyclic GMP-dependent proteinkinase I (cGKI) pathway cannot regulate the cytosolic calcium ([Ca2+]i) dynamic as in RCEs from Wistar Kyoto rats (WKY). We investigated the altered downstream NO target in SHR cells and, since cGKI expression was low, whether the re-expression of cGKIα in SHR RCEs could restore NO calcium responsiveness. We measured [Ca2+]i dynamic by fura2 imaging analysis and cGKI level by RT-PCR and WB in SHR and WKY RCEs. Plasmids encoding for enhanced green fluorescence protein (EGFP) or cGKIα-EGFP were transiently transfected in SHR RCEs and [Ca2+]i was evaluated. Angiotensin-II (AT-II) increased [Ca2+]i in a concentration-dependent way in both strains. Whereas in WKY, endogenously produced NO and cyclic GMP analog decreased AT-II-induced [Ca2+]i transient, they were ineffective in SHR RCEs. The cGKI level was low in SHR cells. However, after cGKIα re-expression, endogenous NO decreased AT-II-induced [Ca2+]i transient, while eNOS and cGKI inhibition prevented it. The cGKI low expression in SHR accounts for the absent regulation of agonist-induced [Ca2+]i transient by NO/cyclic GMP pathway. Studies on cGKI in humans could contribute to a better understanding of cardiovascular pathologies.