Distribution of Radioactivity in Human Maternal and Fetal Tissues Following Administration of C14-4-Progesterone.

Abstract

After the administration of Cl4-4-progesterone to pregnant women the highest concentration of radioactivity was found in the maternal fat. A rough calculation revealed that the fat compartment contained about 17.7% of the administered radioactivity 12 hours, 33.7% 24 hours, and 19.6% 48 hours after administration of the labeled hormone. These findings indicate that progesterone and/or its metabolites diffuse promptly from the blood circulation into the fat compartment of the body. Only moderate amounts of radioactivity were found in the myometrium and the decidua, the two principal target organs of progesterone. Low to moderate concentrations of radioactivity were detected in the organs which serve as principle sources of the hormone, the corpus luteum and the placenta. Radioactivity was present in very small concentrations in all fetal tissues with the exception of the fetal brain and the testes where no radioactivity could be detected. The highest concentration in fetal tissues was found in the fetal adrenal glands.