Effects of Nitric Oxide on Voltage-Gated K+ Currents in Human Cardiac Fibroblasts through the Protein Kinase G and Protein Kinase A Pathways but Not through S-Nitrosylation

초록

This study investigated the expression of voltage-gated K+ (K-v) channels in human cardiac fibroblasts (HCFs), and the effect of nitric oxide (NO) on the K-v currents, and the underlying phosphorylation mechanisms. In reverse transcription polymerase chain reaction, two types of K-v channels were detected in HCFs: delayed rectifier K+ channel and transient outward K+ channel. In whole-cell patch-clamp technique, delayed rectifier K+ current (I-K) exhibited fast activation and slow inactivation, while transient outward K+ current (I-to) showed fast activation and inactivation kinetics. Both currents were blocked by 4-aminopyridine. An NO donor, S-nitroso-N-acetylpenicillamine (SNAP), increased the amplitude of I-K in a concentration-dependent manner with an EC50 value of 26.4 mu M, but did not affect I-to. The stimulating effect of SNAP on I-K was blocked by pretreatment with 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or by KT5823. 8-bromo-cyclic GMP stimulated the I-K. The stimulating effect of SNAP on I-K was also blocked by pretreatment with KT5720 or by SQ22536. Forskolin and 8-bromo-cyclic AMP each stimulated I-K. On the other hand, the stimulating effect of SNAP on I-K was not blocked by pretreatment of N-ethylmaleimide or by DL-dithiothreitol. Our data suggest that NO enhances IK, but not I-to, among K-v currents of HCFs, and the stimulating effect of NO on I-K is through the PKG and PKA pathways, not through S-nitrosylation.

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