title: Role of PKC in the attenuation of the cGMP-mediated relaxation of skinned resistance artery smooth muscle seen in glyceryl-trinitrate-tolerant rabbit.
abstract: We examined whether 10 days' in vivo treatment with glyceryl trinitrate (GTN) might reduce cGMP-induced relaxation in the smooth muscle of rabbit mesenteric resistance arteries and, if so, whether protein kinase C (PKC) plays a role in this downregulation. The relaxation responses to GTN and the nitric oxide donor NOC-7 were significantly reduced in endothelium-denuded strips from GTN-treated rabbits. In beta-escin-skinned smooth muscle, the ability of 8-bromoguanosine 3',5' cyclic monophosphate (8-Br-cGMP, a phosphodiesterase-resistant cGMP analogue) to relax the contraction induced by 0.3 microM Ca2+ was significantly reduced in GTN-treated rabbits. In beta-escin-skinned smooth muscle, an inhibitor of conventional and/or novel PKCs, GF109203X (0.6 microM), inhibited the Ca2+ -induced contraction and enhanced the 8-Br-cGMP-induced relaxation. However, since the relaxing ability of 8-Br-cGMP was found to be unchanged by GF109203X when contractions were amplitude-matched (0.2 microM Ca2+ alone vs 0.3 microm Ca2+ + GF109203X), the increase in the 8-Br-cGMP-response seen with GF109203X was probably due to its inhibitory action on the Ca2+ -induced contraction. Furthermore, although the PKC activator phorbol 12,13-dibutyrate (PDBu, 0.1 microM) decreased the 8-Br-cGMP-induced relaxation of the Ca2+ (0.3 microM) contraction, this was probably due to its enhancement of the Ca2+ -induced contraction since no such effect of PDBu was seen when the Ca2+ -induced contractions were amplitude-matched (0.2 microM Ca2+ + PDBu vs 0.3 microM Ca2+ alone). These results suggest that the relaxing response to cGMP is reduced in the smooth muscle of mesenteric resistance arteries in GTN-treated rabbits but that conventional and/or novel PKCs do not play a major role in maintaining this downregulation. British Journal of Pharmacology (2004) 141, 391-398. doi:10.1038/sj.bjp.0705625
authors.affiliation: Department of Cellular and Molecular Pharmacology,Graduate School of Medical Sciences, Nagoya City University, Nagoya 467-8601, Japan.
authors.forename: Youichirou
authors.initials: Y
authors.lastname: Nakano
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Kusama
authors.forename: Junko
authors.initials: J
authors.lastname: Kajikuri
authors.forename: Yoshikatsu
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kanmura
authors.forename: Takeo
authors.initials: T
authors.lastname: Itoh
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000201:enzymology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology; D005996:Nitroglycerin / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011817:Rabbits; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; C016276:8-bromocyclic GMP; D011493:Protein Kinase C; D005996:Nitroglycerin; D006152:Cyclic GMP