STUDIES CONCERNING THE HORMONAL INDUCTION OF LACTOGENESIS BY PROSTAGLANDIN-F2ALPHA IN PREGNANT RATS

Factors involved in the induction of lactogenesis by prostaglandin F2α in pregnant rats have been studied. PGF2α-tromethamine salt (150 μg × 2) injected on day 18 of pregnancy, induced a significant increase in ovarian 20α-hydroxysteroid dehydrogenase activity with maximal values 24 h after treatment. Simultaneously, serum progesterone concentration starts to decrease significantly 4 h after PGF2α administration. These ovarian changes are related to the significant increase in serum prolactin which occur between 12 and 24 h after prostaglandin treatment. At mammary gland level, specific prolactin binding sites were significantly higher 4 and 8 h after PGF2α administration followed by a rapid decrease to normal values at 12 and 24 h. The effect on placental function was determined by measurement of the chorionic mammotrophin in plasma. No modification was found in chorionic mammotrophin levels in the first 24 h after PGF2α treatment, being the values similar to those in the control rats. Lactogenesis visualized by an oxytocin test, occurred in the pregnant PGF2α treated rats 24 h after the administration of the drug. The described hormonal changes occurring after PGF2α treatment, resemble the physiological events that take place in the control rats before parturition. These results suggest that prostaglandin may play a physiological role in the induction of lactogenesis in pregnant rats. © 1979.