Partial characterization of a uteroglobin-like protein in the human uterus and its temporal relationship to prostaglandin levels in this organ.

During the past decade several corticosteroid-dependent, low mol wt proteins with phospholipase-A2 (PLA2) inhibitory activity have been described. This family of proteins is collectively known as lipocortins. Blastokinin or uteroglobin (utg), a progesterone-induced protein, first discovered in the pregnant rabbit uterus, is also a potent PLA2 inhibitor, but genetically distinct from lipocortins. Although utg has been found in rabbits, its presence in humans has not been well established. Here, we present biochemical, immunological, and immunohistological evidence for the detection of a utg-like protein in the human uterus. Since inhibition of PLA2 may modulate tissue eicosanoid levels and since rabbit utg has been reported to be a potent PLA2 inhibitor, we also studied the temporal relationship between utg and tissue prostaglandin E2 and F2 alpha levels in estrogen- and progesterone-dominated endometrial tissue. We found an inverse temporal relationship between utg-like protein and eicosanoid levels in this organ. Since some eicosanoids (e.g. prostaglandins, leukotrienes, etc.) are known to be involved in smooth muscle contractility and inflammatory processes, our findings may help to understand the pathogenesis of some human disorders in which abnormal eicosanoid production occurs.