Journal of Clinical Endocrinology & Metabolism, Vol 76, 424-428, Copyright © 1993 by Endocrine Society

ARTICLES

Protein kinase-C stimulatory activity in human amnion cytosol

KM Eyster, F Teixeira, T Zakar and DM Olson
Department of Physiology and Pharmacology, University of South Dakota, Vermillion 57069.

Cytosolic preparations from human amnions at term were tested for the presence of endogenous modulators of protein kinase-C (PKC) activity. Tissues were obtained from 14 patients undergoing cesarean section (CS) and 14 patients after spontaneous delivery (SL). PKC activity was significantly greater in cytosols from CS than SL amnion (1.65 +/- 0.04 vs 0.73 +/- 0.2 pmol/min, respectively; mean +/- SE; n = 14 CS; n = 14 SL; P < 0.05). When amnion cytosols were mixed with a control preparation of PKC (rat brain cytosol partially purified on diethylaminoethyl), PKC activity was significantly increased compared to the control value (control, 12.81 +/- 2.1; control + CS, 22.19 +/- 1.5; control + SL, 21.98 +/- 0.7 pmol/min). The stimulation of PKC was dose dependent. The PKC stimulatory factor in amnion cytosol was stable to heat treatment at 80-90 C for 2 min (control + heat-treated CS, 23.20 +/- 1.2; control + heat-treated SL, 24.49 +/- 1.0 pmol/min) and substituted for phosphatidylserine and diacylglycerol in the PKC assay (control, no lipids, 0.05 +/- 0.04 pmol/min; control + amnion cytosol, no lipids, 9.60 +/- 1.06 pmol/min). The PKC stimulatory factor was calcium dependent, was not extractable in organic solvents, and was greater then 100,000 mol wt. Thus, the human amnion contains a PKC stimulatory factor which may modify or mediate the cellular response to extracellular stimulators of the PKC pathway.