Cyclic modulation of integrin expression in bovine endometrium.

Integrins are heterodimeric glycoproteins involved in cell-cell and cell-extracellular matrix adhesion. In this study, the spatial and temporal distribution of selected integrins and extracellular matrix proteins was determined in bovine endometrium from cycling and ovariectomized animals using indirect immunohistochemistry. The expression of integrins alpha(6) and alpha(v)beta(3) was estrous cycle-dependent. Strong immunostaining for alpha(v)beta(3) occurred in the basement membrane region of intercaruncular luminal epithelium except on Day 16 (P<0.05). Staining of subepithelial stromal cells declined in diestrous samples (P<0.05). In all samples, there was reduced alpha(v)beta(3) reactivity in the caruncles. Staining for alpha(6) decreased in the epithelial basement membrane at proestrus through estrus (Days 18-0). Expression of integrin subunits alpha(3) and alpha(4) was cycle-independent. Moderate staining for alpha(3) was detected on epithelium and alpha(4) was present on stromal cells. The distribution of beta(1) suggested dimerization with alpha(3), alpha(4), and alpha(6). Laminin was detected in the epithelial and vasculature basement membranes. Collagen IV was present in the glandular epithelium basement membrane and subepithelial stromal cells, whereas fibronectin was found only in the stroma. Estrous cycle-dependent distribution and expression of alpha(v)beta(3) and alpha(6) suggest their regulation by ovarian steroids, growth factors, and prostaglandins.