Whole body autoradiographic distribution studies on nonionic x-ray contrast agents in pregnant rats

The time course of the distribution of radioactive label in organs and tissues was investigated after intravenous administration of iotrolan, iopamidol, iopromide, and iohexol in a concentration of 60 mg I/ml (2.2 MBq 125I/mg I) as aqueous solution to pregnant rats (18th day after conception) by a whole-body autoradiographic technique. All contrast agents were rapidly distributed within the organism, showing equal distribution patterns of radioactivity, and were rapidly excreted, mainly by the kidney. Passage of radioactivity across the blood-brain and placental barriers could not clearly be shown. No specific and long-lasting retention of radioactivity could be seen in any organ or tissue with the exception of the thyroid.