Oophorectomy and Maintenance of Pregnancy in the Rat

It is generally agreed that removal of the ovaries during pregnancy, in the rat, invariably results in the untimely interruption of this condition. 1 - 4 Evidence is presented in this report, however, which demonstrates that under certain experimental conditions this rule does not hold, and that the rat may carry through to term during the latter part of pregnancy in the entire absence of ovarian tissue.

Adult female rats were subjected to unilateral resection of a Fallopian tube, to insure an initial litter size reduction. This was followed by exactly time mating. Laparotomy, performed on the 12th or 13th day of pregnancy, involved removal of one ovary and of foetuses in the fertile horn in excess of one. Foetal removal was so effected as to leave the placentae intact and in situ. Two days later in each instance the remaining ovary was ablated. Of 10 animals used in this series all carried to term, but failed to deliver, and the young were recovered alive after being allowed to remain in utero for one and 2 days past the expected date of parturition. Placentae, including those of previously removed foetuses, were viable and healthy.

A second group of 10 females was subjected to precisely the same treatment, with the exception that the ‘extra’ placentae were included in the surgical removal of foetuses on the 12th or 13th day. Following removal of the second ovary none carried to term. Autopsy on the expected date of delivery revealed markedly involuted uteri containing no indications of embryonic substance. A control group of 11 animals, treated in the same manner with the exception that the second ovary was not extirpated, carried through successfully, and normal delivery occurred in each instance at the expected time.