Stimulation of creatine kinase activity by calcium-regulating hormones in explants of human amnion, decidua, and placenta

We have used stimulation of the activity of the brain type creatine kinase (CK) isoenzyme as a response marker to examine the effects ofvitamin D metabolites, PTH, and calcitonin in cultured explants of placenta, decidua, and amnion from normal human deliveries. We found a biologicalresponse to PTH in placenta and amnion and to vitamin D metabolitesinall three tissues. In the amnion, CK activity increased 2.3- foldafter 24 h of incubation in 2.5 nM 1,25-dihydroxyvitamin D3 [1,25-(OH)₂D₃], 3.8-fold when incubated with 12.5 nM 24,25- dihydroxyvitamin D₃ [24,25-(OH)2D3] and 2.7-fold when incubated with 10 U/l bovine PTH. In the decidua, 24,25-(OH)₂D₃ but not 1,25-(OH)₂D₃ or bPTH caused a 1.7-fold increase in CK activity. In contrast, the placenta responded to 1,25-(OH)₂D₃ with a 1.6-fold increase in CK activity and to bPTH, with a 1.7- fold increase but did not respond to 24,25-(OH)₂D_3. Bovine calcitonin (100 ng/ml) had no effect on CK activity in any of the three tissues. Nearly all CK in both the unstimulated and stimulated explants was the brain type isoenzyme. CK activity increased significantly between 1 and 4 h after hormonal treatment in all experiments. The enzyme activity rose steeply with dose and reached a significant increase, and usually a plateau, at hormone concentrations considered to be physiological in vivo. [³H]Thymidine incorporation into DNA increased in parallel to stimulation of CK activity in all experiments, except that PTH did not increaseDNA synthesis in the placenta. PTH did cause an increase in cAMP production in explants of amnion (1.5-fold) and placenta (2.6-fold).