The distribution of radioactivity in pregnant rats after repeated oral doses of the diuretic agent Etozolin.

1. The distribution of radioactivity has been studied by whole-body autoradiography after administration of daily oral doses of (2-14C)-ethyl (Z)-(3-methyl-4-oxo-5-piperidino-thiazolidin-2-ylidene)acetate (etozolin, Gö 687, Elkapin) at a dose level of 100mg/kg to pregnant rats during the 10th to the 17th day of gestation. 2. After the last dose, most of the radioactivity was excreted rapidly and was mainly assoicated with the gastrointestinal and urinary tracts and kidneys of the mothers. 3. Maximal distribution in the mothers occurred at 3--6 h after the last dose, and radioactivity at these times was detectable also in the lungs, muscle mass, fat, mammary and uterine tissue, the reticuloendothelial system, placentae, some ducted and endocrine glands, and in blood, but not in brain or spinal cord. At 4 days, traces of radioactivity had persisted in kidneys, liver, lungs, thyroid and placentae. 4. Radioactivity was present in low and uniform concentrations in most foetal tissues such as the heart, lungs and lens and in even lower concentrations in the brains of the foetuses during 3--6 h after dosing, but was not detected in foetal tissues at 2 days. Concentrations of radioactivity in maternal tissues were at all times much higher compared with those in foetal tissues at corresponding times after dosing.