Factors Which Affect the Relative Contributions of Ovarian and Uterine Arteries to the Blood Supply of Reproductive Organs in Guinea Pigs1

Abstract

The contributions of the ovarian and uterine arteries to the arterial supply of uterus and ovaries was studied in guinea pigs on Days 0, 3, 4, 7 and 11 of the estrous cycle and Day 11 of pregnancy (Exp. 1) and on Days 7 and 11 of diestrus and pregnancy (2 × 2 factorial, Exp. 2). Methodology involved simultaneous injection of microspheres labeled with different isotopes into the left ventricle (A-spheres) and into the aorta between the origins of ovarian and iliac arteries (B-spheres). In all guinea pigs, the ovaries and oviducts contained only A-spheres indicating that the ovarian artery provided all of the arterial supply on all days studied. The ratio of A/B spheres was not significantly different between the cervix and caudal third of the uterus and it was assumed, therefore, that the uterine artery provided all of the arterial supply. The A/B ratio was significantly greater for the cranial third of the uterus than for the middle third and was greater for the middle third than for the caudal third. The percent blood contributed by the ovarian artery was calculated to be 90 percent for the cranial third and 44 (Exp. 1) and 42 percent (Exp. 2) for the middle third. These results demonstrated that the direction of blood flow in the prominent uteroovarian arterial anastomosis was toward the uterus. In Exp. 2, the percent contribution of the uterine artery to the blood supply to the cranial third of the uterus increased when the guinea pigs became pregnant especially on Day 11 and on the side ipsilateral to the ovary with the greater number of CL presumably reflecting the development of implantation sites. The contribution of each artery to the blood flow to each organ or segment of the reproductive tract was also expressed in Exp. 2 as a percent of blood flow to the kidneys. The contribution of the ovarian artery to blood flow to the cranial and middle segments of the uterus increased significantly toward the end of diestrus. The contribution of the uterine artery to the middle segment increased significantly at Day 11 in pregnant guinea pigs. An analysis of the contribution of each artery (ovarian and uterine) to the total blood flow summed over all genitalia (ovaries, oviducts and uterine horns) indicated that on both Days 7 and 11 the ovarian artery was the major contributor in cycling guinea pigs, whereas in pregnant guinea pigs at Day 11, the uterine artery was the major contributor. The supply from the principal contributing artery (ovarian artery in cycling guinea pigs, uterine artery in pregnant guinea pigs) was greater at Day 11 than at Day 7. These results indicate that the mechanisms for increased blood flow to the paired genitalia in late diestrus were exerted through the ovarian artery. However, on the corresponding day of pregnancy the mechanisms for increased flow were exerted through the uterine artery.