Distribution of ova in the rat uterus.

Abstract

Both ovaries of female rats were exteriorized and, with the remainder of the rat in a protective lead shield, were subjected to 800 r of x rays at 60 days of age. Comparable irradiation was given to only the left ovary in other animal and some of these were unilaterally castrnted by the removal of the right ovary. In others, unilateral ovariectomy was done without irradiation of the left ovary. Other females were untreated. Distribution of implantation sites was recorded in 86 pregnancies, of which 44 were first pregnancies. Explorations revealed implantations in a total of 123 uterine horns out of a possible 162. The number of ova in a given horn varied from one to 14. The average was 7.8 ova in a single horn in 60 pregnancies produced by untreated ovaries, and 4.2 in a single horn in 63 pregnancies produced by irradiated ovaries. Although irradiation reduced the average number of implanting ova, the distribution patterns in those uteri supplied by irradiated ovaries were not affected. This reduction resulted in 27 uterine horns having only one or two implantation sites. In contrast, owing to irradiation or to unilateral castration, the opposite ovary produced 9 or more implantations inmore » 29 pregnancies. This incidence of either a smaller or larger number of implantations in a single uterine horn is significantly greater (45%) than normal. Distribution was not related to the number of implanting ova. Slightly more than half of the uterine horns had regular spacing. Irregularities were numerous. There was a tendency for ova to implant more frequently in the cervical half of the uterus. It is suggested that distribution is dependent on random scatter at the time implantation is initiated.« less