Relationship of luteal blood flow and corpus luteum function in pseudopregnant rats

An experiment was conducted to examine whether blood flow to corpora lutea may regulate luteal function as judged from plasma levels of progesterone (P) in mature pseudopregnant rats. 141Ce-labeled microspheres (14.1 +/- 0.8 micrometer diam) were used to measure cardiac output and organ and tissue blood flow in rats on days 6, 8, 10, and 12 of pseudopregnancy and in proestrus following luteal regression. The mean arterial blood pressure and cardiac output were similar among all groups of rats. Although a significant (P less than 0.05) decrease in plasma P was observed in rats on day 12 of pseudopregnancy, no change in luteal blood flow or distribution of ovarian blood flow to the corpora lutea was seen at this stage of pseudopregnancy when compared to day 8 or 10 of pseudopregnancy. However, a significant decrease (P less than 0.05) in luteal blood flow was seen in proestrous rats. Because a decrease in plasma progesterone preceded the decrease in luteal blood flow, it was concluded that physiological luteal regression may not be initiated by a reduction of blood flow to the corpus luteum.