Prolactin stimulates creatine kinase activity and DNA synthesis in explants of human amnion

To characterize the action of hPRL and human placental lactogen on the amnion, decidua and placenta, we examined the effects of these hormones on the brain type isozyme of creatine kinase in cultured explants of these tissues from normal deliveries. In the amnion, hPRL (1 mg/l) caused a 1.8-fold increase in creatine kinase specific activity in 24 h, whereas hGH (1 mg/l) or human placental lactogen (1 mg/l) had no effect; oPRL (1 mg/l) also caused a 2.5-fold increase in creatine kinase activity. Neither hPRL, human placental lactogen nor hGH had a significant effect on creatine kinase activity in the placenta or decidua. [3H]thymidine incorporation into DNA increased in parallel to the stimulation of creatine kinase activity. The predominant isozyme of creatine kinase in both the unstimulated and stimulated explants was the brain type isozyme. Creatine kinase activity in the amniotic tissue increased significantly 2 h after hPRL treatment and reached its highest value at 4 h. The enzyme activity in the amnion rose with increasing hPRL dose and showed a significant increase at physiologic concentrations as low as 0.01 mg/l. This study, therefore, provides evidence for biological action of prolactin in amniotic tissue, suggesting that the amnion is physiologically responsive to prolactin.