Abstract

PIP: To determine the importance of placental lactogen in pregnancy, 45 of 205 inbred Buffalo rats studied were injected with an antibody against human placental lactogen (HPL) produced in rabbits. 100 rats were studied simultaneously as untreated controls, 40 rats were injected intraperitoneally with .5 ml. of anti-HSA, and 20 rats were injected intraperitoneally with .5 ml. of NRS as treated controls. All rats were mated and pregnancies were determined by the presence of sperm in vaginal washes. All of the control groups produced normal litters, while none of the rats injected with anti-HPL delivered. Examination on Day 27 of pregnancy revealed that implantation apparently had taken place, followed by deterioration and destruction of the fetal tissue. 20 of these anti-HPL treated rats were followed after treatment and normal estrous cycle did recur. Some of these rats continued to be impregnated by males for up to 11 months, but no pregnancies occurred. The absolute antipregnancy effect of this treatment is highly significant, and the continuing long-term antiimplantation effect is surprising. It is concluded that the evidence supports the universality among animals of placental lactogen as an integral part of successful pregnancy, and that further research may develop an immunological contraceptive technique with this antibody.