Uteroglobin: a phospholipase A2 inhibitory protein in rabbit blood

Abstract

Uteroglobin(utg) is a potent phospholipase A2 inhibitor but is genetically distinct from lipocortins. The purpose of the present investigation was to biochemically and immunologically characterize the utg-like antigen from rabbit plasma and serum that were found to be highly positive by radioimmunoassay(RIA). The RIA standard curve of pure rabbit utg from the uterus is compared with utg-like protein in circulation, and the curves are parallel to each other. Concerning the western blot of utg-like protein as compared with utg standard, it is clear that there is a distinct protein band corresponding to the two monomers of utg(7 kDa). Moreover, the rise in endometrial utg synthesis that occurs upon progesterone(P) treatment in rabbits is paralleled by a dramatic decrease in endometrial PGE2, PGF2 alpha levels. The level of utg-like protein in circulation increased the level of this protein approximately three-fold in the serum (70 ng/ml without Pvs 216 ng/ml with P), whereas dexamethasone(Dex) increased it two-fold. To determine the source of this protein in circulation, we cannulated the uterine and the pulmonary veins of rabbits primed with different steroids. The levels of utg-like protein in the uterine venous plasma versus peripheral venous plasma were as follows: 379 ng/ml vs 216 ng/ml, treated P. The pulmonary venous plasma was compared with the peripheral venous samples (1240 ng/ml vs 127 ng/ml, treated Dex). The results of the present study indicate that utg-like protein is detectable in the circulation of the rabbit.