Direct pharmacologic and osmolal effects of contrast media on the mechanics of heart muscle isolated from cats. 
We studied 56 right ventricular papillary muscles isolated from cats to determine whether the direct mechanical effects of contrast media are due to their pharmacologic action or to the hyperosmolality caused by them.  A 10% solution of Renografin-76 abruptly decreased force 22% below control, then slowly increased it to 22% above control.  To elucidate these changes we also studied: (1) Renografin-60 (lower concentration of diatrizoate); (2) meglumine and diatrizoate; (3) meglumine alone; (4) diatrizoate sodium; (5) ethylene diamine tetra-acetic acid (EDTA) (same concentration as in Renografin-76); (6) sucrose to increase osmolality; and (7) Amipaque (metrizamide), a contrast medium without meglumine or diatrizoate.  All solutions containing meglumine, and EDTA alone decreased force.  Diatrizoate sodium also decreased force initially, presumably due to the high sodium concentration.  Meglumine alone decreased force abruptly and substantially.  In contrast, metrizamide and 100 mmol sucrose only increased force.  Thus, the abrupt decrease in force was caused by the pharmacologic action of meglumine, EDTA, or high sodium in the contrast media, whereas the slow increase in force was caused by hyperosmolality.