Activities of Ca2+-ATPase and Na+ + K+-ATPase in human placenta

Although there have been a few reports on Ca2+-ATPase and Na+ + K+-ATPase in human placenta, they are still insufficient for getting more detailed information about human placenta. In this study we investigated some characteristics of the Ca2+-ATPase and measured the activity of Ca2+-ATPase and Na+ + K+-ATPase at various gestational periods. Maximum activity of Ca2+-ATPase was seen at 3 mM and pH 9.0. The enzyme was distinguished from ALP (i.e., Alkaline phosphatase) by such tests as adding L-phenylalanine and heat treatment. Our measurement results of Ca2+-ATPase activity (mumoles Pi/mg protein/30 min) in human placental chorion were 21.9 +/- 2.4 (Mean +/- S.D.) at 10-15 gestational weeks, 19.1 +/- 1.4 at 16-27 gestational weeks, 31.4 +/- 7.2 at 28-35 gestational weeks, and at 36-42 gestational weeks, the AFD group showed 25.8 +/- 4.6, the LFD group, 27.9 +/- 2.1, and the SFD group, 21.2 +/- 1.9. Those of Na+ + K+-ATPase activity (mumoles Pi/mg protein/30 min) were 0.98 +/- 0.05 at 10-15 gestational weeks, 0.82 +/- 0.02 at 16-27 gestational weeks, 1.85 +/- 0.42 at 28-35 gestational weeks and at 36-42 gestational weeks, the AFD group showed 1.58 +/- 0.45, the LFD group, 1.49 +/- 0.37, and the SFD group, 1.68 +/- 0.36. As a result, Ca2+-ATPase activity tended to be higher at 28-35 gestational weeks than for other periods, while it showed lower for the SFD group than for the AFD group. As regards to Na+ + K+-ATPase activity, there were not seen any significant differences between the AFD placenta and the LFD placenta as compared with the AFD placenta.