ROLE OF INTRACELLULAR CALCIUM STORES IN CONTRAST MEDIUM-INDUCED RENALVASOCONSTRICTION

Rationale and Objectives. Renovascular smooth muscle contractility, an important factor in contrast media-induced nephrotoxicity, depends on intracellular Ca2+ concentration, which is composed of extracellular Ca2+ influx and intracellular Ca2+ release. These factors were investi gated in contrast media-induced renal vasoconstriction in an in vitro model. Methods. KCl-induced isometric contractions of rabbit renal art ery were compared with contractions elicited by contrast media (diatri zoate, iohexol, iopamidol). Measurements were made after incubation wi th the Ca2+ channel blockers nifedipine, verapamil, and diltiazem to a ssess the role of extracellular Ca2+ influx and after ryanodine and th apsigargin to investigate the role of intracellular Ca2+ release. Resu lts. The Ca2+ channel blockers partially inhibited contractions induce d by contrast media, while KCl-induced contractions were completely ab olished. Ryanodine and thapsigargin also markedly inhibited contrast m edia-induced contractions. Conclusion. Ionic and nonionic contrast med ia induced quantitatively different renal vasocontractions. Ca2+ chann el blockers inhibited this vasocontraction only slightly compared with intracellular Ca2+ release blockers.