ABSTRACT
In this study we investigated if sodium nitroprusside (NaNP), a vasodilator with direct action on smooth muscle, would have any effect on calcium kinetics in blood vessels. The effect of NaNP, in 0.1-10 micrometer concentration, was studied in vitro on the uptake of 45Ca with the lanthanum method and on the efflux of 45Ca. The drug failed to alter the uptake of 'La-resistant' 45Ca in rabbit mesenteric artery and vein. This was true even if Ca2+ uptake was increased in the vessels by 60 mM KCl. The efflux of 45Ca on the other hand was enhanced from rabbit mesenteric vein and from rat aorta exposed to NaNP, in a dose-related way. The present study, like our previous one on other vasodilators, indicates that NaNP has en effect on vascular calcium kinetics but this is the first time that a relationship could be established between the dose of the drug and the effect on 45Ca efflux.
Subject(s)
Blood Vessels/metabolism , Calcium/metabolism , Ferricyanides/pharmacology , Nitroprusside/pharmacology , Animals , Aorta/drug effects , Aorta/metabolism , Calcium Radioisotopes , In Vitro Techniques , Male , Mesenteric Arteries/drug effects , Mesenteric Arteries/metabolism , Mesenteric Veins/drug effects , Mesenteric Veins/metabolism , Potassium Chloride/pharmacology , Rabbits , Time FactorsABSTRACT
In the search for abnormalities in hypertensive vessels Ca kinetics was studied in the aorta of spontaneously hypertensive rats (SHR). The uptake of 45Ca was significantly less in hypertensive animals but the uptake of 'Lanthanum resistant' 45Ca was not. The efflux of 45Ca from aorta of SHR was different (P less than 0.01) from that of control rats because of faster initial efflux. The half-life of the first 2 components of efflux curves was significantly shorter in SHR. Results are interpreted as consequences of decreased Ca binding by smooth muscle membrane in hypertensive vessels.
