AN ENDOGENOUS INHIBITOR OF PROSTAGLANDIN SYNTHESIS IN HUMAN DECIDUA

Human first trimester decidual tissue has been reported to contain an inhibitor of cyclo-oxygenase enzyme, but a careful reading of the lite rature indicates that the inhibitor may be human albumin. Our own stud ies also showed that high levels of albumin were present in samples fr om homogenised decidual tissues. We therefore digested the tissue to o btain isolated cells and washed them extensively to minimise contamina tion with blood. Homogenates of such cells did not bind arachidonic ac id, and inhibited cyclo-oxygenase enzyme-1 (COX-1) activity. The cellu lar factor inhibited COX-1 at concentrations of 60-100 mu g protein/ml , and was therefore more potent than human albumin (0.5-2.0 mg/ml). Th e inhibitory activity was lost after heat treatment (100 degrees C for 10 mins) and after digestion with trypsin or papain, but was resistan t to mercaptoethanol and urea. Preliminary data indicated that the pro tein had a molecular weight >30 kD.