In this study, we identify and investigate the role of protein kinase G (PKG) in cells cultured from human prostatic stroma. Cells were used for immunocytochemistry, contractility or K+ fluorescent imaging studies. All cultured prostatic stromal cells showed PKG immunostaining, Phorbol 12,13 diacetate (PDA, 1 muM) elicited contractions from human-cultured prostatic stromal cells that could be blocked by both the L-type Ca2+ channel blocker. nifedipine (3 muM), and the protein kinase C inhibitor, bisindolylmaleimide (1 muM). The nitric oxide donor, sodium nitroprusside (SNP, molar pIC(50) 5.16 +/- 0.17) and the cGMP-phosphodiesterase inhibitor, zaprinast (50 muM), inhibited PDA (1 muM)-induced contractions, The PKG activator beta-phenyl-1, N-2-ethenoguanosine-3',5'-cyclic monophosphate (PET-cGMP. molar pIC(50) 6.96 +/- 0.25) also inhibited PDA (1 muM)-induced contractions. Glibenclamide (10 muM) and Rp-8-Br-cGMPS (5 muM), but not iberiotoxin (100 nM) or Rp-cAMP (5 muM), reversed this inhibition, In human-cultured prostatic stromal cells loaded with the K+ fluorescent indicator, 1,3-Benzenedicarboxylic acid, 4,4'-[1,4,10,13-tertraoxa-7,16-diazacyclooctadecane-7,16-diylbis(5-methoxy-6,2-benzofurandiyl)] bis-, tetrakis [(acetyloxy) methyl] ester (PBFI), PET-cGMP (300 nM) caused a reduction in intracellular K+ that was blocked by glibenclamide (10 muM) and Rp-8-Br-cGMPS (5 muM), but not by iberiotoxin (100 nM). These data are consistent with the hypothesis that, in human-cultured prostatic stromal cells, PKG inhibits contractility through the activation of K-ATP channels. (C) 2002 Elsevier Science Inc. All rights reserved.
