title: The effect of hydroxocobalamin on the nitroprusside-induced relaxation of rat aortic preparations.
abstract: Hydroxocobalamin (HOCb) when mixed with sodium nitroprusside (SNP) in a 10:1 or 1:1 molar ratio had no significant effect on the relaxation of noradrenaline-precontracted rat aortic rings. However, the addition of HOCb did prolong the time taken for the relaxant response to occur. The time taken for a 0.34 microM SNP dose to exert 50% of its relaxant effect was increased by about 120 and 35% with 10:1 and 1:1 HOCb/SNP molar ratio mixtures, respectively. A 0.5:1 HOCb/SNP molar ratio mixture caused no prolongation. In incubations with [14C]SNP, it was found that mixing with equimolar, or greater, amounts of HOCb, reduced aortic tissue uptake of radioactivity. The results support the hypothesis that both SNP alone and SNP/HOCb complexes breakdown extracellularly to release the same amount of active species, but that in the case of the complexes the active agent is released at a slower rate.
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects; D004347:Drug Interactions; D005292:Ferricyanides / Q000494:pharmacology*; D006879:Hydroxocobalamin / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D005292:Ferricyanides; D009599:Nitroprusside; D006879:Hydroxocobalamin