Inhibition of prostaglandin synthase by maternal plasma factor(s) in early human pregnancy.

Using an enzyme incubation-radioimmunoassay technique, we have tested the hypothesis that an increase in a maternal plasma factor(s) that inhibits prostaglandin synthase (EC 1.14.99.1) is responsible for the suppression of decidual prostaglandin production that occurs in early human pregnancy. Measurements made on serial maternal samples failed to reveal any significant increase in plasma inhibitory activity at this time, and it was concluded that the conceptus achieves the reduction in prostaglandin synthesis by a mechanism other than a systemically mediated direct inhibition of decidual prostaglandin synthase.