α1‐ANTITRYPSIN — COMPLEXATION AND INACTIVATION IN THE UTERINE FLUID OF IUD‐USERS

Electrophoretic homogeneity of α1‐antitrypsin (α1‐AT) was studied in the uterine fluid from two groups of normal women; one group was comprised of IUD‐users, the other on non‐users. α1‐AT was found in its free and active form in non‐users. In IUD‐users, one fraction was complexed by granulocyte elastase and neutral proteinase. The other fraction had the same electrophoretic mobility as the native inhibitor, but was inactive, as determined from trypsin inhibition studies. This may explain the finding of elastase activity together with non‐complexed α1‐AT in some samples from IUD‐users. It is concluded that uterine fluid in IUD‐users possesses a minimal, if any, proteinase inhibiting potential. Non‐inhibited activity of granulocyte proteinases in the uterine cavity may incluence hemostasis of the endometrium.