Hormonal control of plasma and erythrocyte volumes of rat uterus

Abstract

The hyperemic response of rat uterus to estrogen was studied in spayed and intact animals by labeling plasma and erythrocytes with radioisotopes. Animals were frozen in liquid nitrogen and uteri dissected in the frozen state to prevent loss of blood. Volumes per 100 mg dry tissue were calculated from radioactivity measurements. Circulation time studies were done on spayed animals to determine the amount of plasma label lost to extravascular space before and after estrogen treatment. Volume determinations were also done on uteri at room temperature for comparison to values obtained from frozen uteri. Plasma volume increased 125% of the control value 3 hours after a single injection of 2 µg estradiol-17-ß after correction for plasma label located in extravascular space. Erythrocyte volume increased only 60% which resulted in a decrease in hematocrit from 37.68% to 28.40%. A similar decrease in hematocrit was found in intact animals just prior to stage 1 of the estrous cycle. Possible explanations for the decrease were considered.