title: Inhibition of nitric oxide synthase and soluble guanylate cyclase induces cardiodepressive effects in normal rat hearts.
abstract: Exogenous nitric oxide (NO) has been shown to modulate the contractile force of rat cardiac myocytes. We sought to determine whether endogenous NO-production in the isolated normal rat heart has an effect on myocardial contractility. Hearts of male Wistar rats were investigated using a constant flow perfused non-paced Langendorff preparation. Changes of contractile parameters such as left ventricular peak pressure, dP/dtmax and dP/dtmin, and of coronary perfusion pressure and heart rate were recorded after infusion of the NO-synthase inhibitors N(omega)-nitro-L-arginine (L-NOARG, 0.1 mM, 1.0 mM, n = 6), N(omega)-methyl-L-arginine (L-NMMA, 0.1 mM, 1.0 mM, n = 9) and methylene blue (2 microM, 20 microM, n = 6), the NO-donor sodium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolat (DEA/NO, 0.01 microM, 0.1 microM, n = 12), the specific inhibitor of soluble guanylate cyclase 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 0.1 microM, n = 7) and L-arginine (0.1 mM, 1.0 mM, n = 6). All NO-synthase inhibitors reduced the contractile function of the ventricular muscle before changes in coronary perfusion pressure were evident. The negative inotropic effect of L-NMMA was absent in the presence of an equimolar concentration of L-arginine. ODQ reduced contractile force and coronary perfusion pressure in parallel. By contrast, L-arginine and DEA/NO improved the contractile force of the left ventricle and DEA/NO decreased coronary perfusion pressure. Heart rate was reduced by L-NOARG (1 mM) and methylene blue (20 microM), while DEA/NO (0.1 microM) and L-arginine (1 mM) had a positive chronotropic effect. All these changes were significant (P < 0.05). These results suggest that endogenous NO-production exerts a positive effect on myocardial contraction that is mediated by activation of guanylate cyclase. In addition, NO might be involved in regulation of heart rate.
authors.affiliation: Institut für Pharmakologie, Medizinische Einrichtungen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Kojda
authors.forename: K
authors.initials: K
authors.lastname: Kottenberg
authors.forename: E
authors.initials: E
authors.lastname: Noack
mesh_terms: D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003864:Depression, Chemical; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase