A COMBINED ISOTOPIC AND ELECTRON MICROSCOPIC STUDY OF THE RESPONSE OF THE RAT UTERUS TO EXOGENOUS OESTRADIOL

Abstract

SUMMARY Experiments with 131I-labelled albumin showed that the injection of oestradiol-17 β induces massive escape of fluid with a protein content similar to that of plasma into the extravascular tissue of the uterus of immature female rats. Histological and electron microscopic examination confirmed the increased permeability to protein of uterine blood vessels, and showed its morphological basis to be the appearance of transient and reversible gaps in the normally complete endothelial lining of capillaries and small venules. These gaps were similar to those seen in small blood vessels in acutely inflamed tissues. The ultrastructural appearance of endothelial cells was unchanged in the early phase of the response to oestrogen, but 24–48 hr. later there was electron microscopic evidence of both growth and marked secretory activity of endothelial cells. The nature of the material secreted, if any, has not been determined.