Uterine Distention and Maintenance of Pregnancy Following Oophorectomy in the Rat.

Abstract

One of the writers has reported that removal of ovaries in the rat. need not result in interruption of pregnancy, provided but one fetus be retained and that the placentae of removed fetuses be left in situ. On the basis of this finding, it was suggested that the placentae exercise some degree of endocrine function in the maintenance of gestation—not so well developed, perhaps, as in certain monotocous forms in which the ovaries may be dispensed with during an appreciable part of pregnancy, but sufficiently so that a number of placentae can maintain the gestation of a single surviving fetus; for further discussion reference may be made to the original paper. Now, in view of the striking effects on uterine growth and development that have been reported to follow experimental distention, , the suggestion was advanced that distention might prove a factor in maintenance of pregnancy under such experimental conditions; the investigation of this possibility has led to the present report. The procedure followed was similar to that employed in the earlier work. That is, rats were mated and at a definite time in pregnancy (13th-18th day) were subjected, under ether anesthesia, first to unilateral oophorectomy and removal of fetuses and placentae in excess of one, followed in 2 days by extirpation of the second ovary; in our experience one-stage operations almost invariably result in abortion, as exemplified by the last 4 cases in Table I. In fetal removal small incisions at the implantation sites allowed for “shelling out” of uterine contents, which then were replaced by equivalent masses either of melted paraffin (m.p. 40°C) or of malleable wax. The incisions were closed, and observations were made at suitable times.