Abstract: | Rat gastric membranes enriched in (H+-K+)-ATPase, when prepared in the presence of 1 mM ethyleneglycol-bis-(β-aminoethyl ether)N,N′-tetraacetic acid, showed the ability to accumulate H+ ions upon addition of ATP, KCl, and valinomycin. The membranes were largely impermeable to K+ and Cl?. In contrast, the rat membranes prepared without the Ca2+ chelator lost the ability to develop a pH gradient because of the membrane leakiness to H+. A majority of these membrane vesicles became also permeable to K+. We suggest that the calcium chelator preserved the gastric membrane permeability barrier during isolation by inhibiting various Ca2+-dependent phospholipases in rat gastric mucosa. |