Stage-dependent redistribution of the V-ATPase during bovine implantation

The 16-kD subunit of the vacuolar H+-ATPase (V-ATPase), or ductin, is essen tial for the activity of this proton pump and has roles in intercellular co mmunication and control of cell growth and differentiation. The V-ATPase is important for acidification-dependent degradation of tissue matrices throu gh which some cell types move, and for pH regulation across some epithelial cell layers. Placentation involves intricate signaling, cell proliferation , and controlled invasion. We examined the distribution of three subunits o f the V-ATPase in bovine trophoblast and endometrium at the time of implant ation to determine the relationship of ductin expression to that of two oth er subunits, A (approximately 73 kD) and B (approximately 58 kD). Epithelia l expression of all three subunits was observed, and in nonpregnant animals this expression was apical. As pregnancy proceeded, expression of all subu nits became pericellular in luminal but not glandular epithelium, suggestin g a redistribution of V-ATPase activity. The trophoblast expressed all thre e subunits during initial contact with the epithelium. In the stroma, ducti n expression was reduced after implantation, and we discuss the possibility that ductin plays a role in the shifting communication between stromal and epithelial cells induced by embryo attachment.