Lack of effect of a progesterone-containing silastic IUD on endometrial blood flow in rats

The endometrial blood flow in rats at the site of a progesterone-containing silastic IUD was compared to that from empty horns or horns containing an empty IUD. The blood flow was determined by injecting 85krypton saline into the aorta and measuring the clearance from the endometrium with two mini Geiger-Müller tubes inserted into the uterine lumen. The endometrial blood flow around the hormone-containing IUDs was 0.81 ml g-1 min-1. This flow was not different from that found in the two other experimental situations, indicating that blood flow changes is not a major mode of action of either progesterone-containing IUDs or empty silastic IUDs.