8-bromoguanosino-3--5--cyclic-monophosphorothioate and 3-(5--hydroxymethyl-2--furyl)-1-benzylindazole

In rat hepatocytes, atrial natriuretic peptide (ANP) elevates cGMP through activation of particulate guanylyl cyclase and attenuates Ca(2+) signals by stimulating net plasma membrane Ca(2+) efflux. We show here that ANP-stimulated hepatocyte Ca(2+) efflux is mediated by protein kinase G (PKG) isotype I. Furthermore, we show that ANP recruits endogenous PKGIalpha, but not PKGIbeta, to the plasma membrane. These effects are mimicked by 8-bromo-cGMP, but not by the soluble guanylyl cyclase activators, sodium nitroprusside and YC-1. We propose that ANP, through localized cGMP elevation, promotes plasma membrane recruitment of PKGIalpha, which, in turn, stimulates Ca(2+) efflux.

Topics: Animals; Atrial Natriuretic Factor; Calcium; Cell Membrane; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic GMP-Dependent Protein Kinases; Hepatocytes; Indazoles; Male; Nitroprusside; Rats; Rats, Wistar; Thionucleotides

Nitric oxide (NO) donors and protein kinase G (PKG) acutely up-regulate K-Cl cotransporter-1 and -3 (KCC1 and KCC3) mRNA expression in vascular smooth muscle cells (VSMCs). Here, we report the presence, relative abundance, and regulation by sodium nitroprusside (SNP) of the novel KCC3a and KCC3b mRNAs, in primary cultures of rat VSMCs. KCC3a and KCC3b mRNAs were expressed in an approximate 3:1 ratio, as determined by semiquantitative RT-PCR analysis. SNP as well as YC-1 and 8-Br-cGMP, a NO-independent stimulator of soluble guanylyl cyclase (sGC) and PKG, respectively, increased KCC3a and KCC3b mRNA expression by 2.5-fold and 8.1-fold in a time-dependent manner, following a differential kinetics. Stimulation of the NO/sGC/PKG signaling pathway with either SNP, YC-1, or 8-Br-cGMP decreased the KCC3a/KCC3b ratio from 3.0+/-0.4 to 0.9+/-0.1. This is the first report on a differential regulation by the NO/sGC/PKG signaling pathway of a cotransporter and of KCC3a and KCC3b mRNA expression.

Topics: Animals; Cells, Cultured; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Gene Expression Regulation; Guanylate Cyclase; Indazoles; Muscle, Smooth, Vascular; Nitric Oxide; Nitroprusside; Protein Isoforms; Rats; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Signal Transduction; Soluble Guanylyl Cyclase; Symporters; Thionucleotides