Effects of contrast media on calcium transients and motion in cultured ventricular cells.

To investigate the mechanisms of the negative inotropic effects of contrast media, we superfused spontaneously contracting cultured chick embryo ventricular cells with Renografin-76 and iohexol (12% solutions), and hypertonic sucrose during simultaneous measurement of [Ca2+]i transients (indo-1) and motion (video-motion detector system). Exposure to contrast agents caused a significant reduction of contractility, with Renografin-76 having a much greater effect on amplitude of motion than iohexol. Renografin-76 significantly depressed [Ca2+]i transient amplitude, whereas iohexol had no effect. Addition of Ca2+ to correct for calcium binding by Renografin-76 completely reversed its depression of [Ca2+]i transients but only partially reversed the negative inotropic effects. Hypertonic sucrose caused a significant decrease in contraction amplitude, with no significant effects on [Ca2+]i transient amplitude. We conclude that the marked negative inotropic effect of Renografin-76 is caused by both calcium binding and hypertonicity. The less marked depression of contractility produced by iohexol likely is a result of hypertonicity and not caused by alteration of [Ca2+]i.