Parotid acini were isolated and tested to further establish the presence of ecto-ATPase in the intact cells. Inhibitors were used to determine if the inhibitor profile of the ATPase was similar to that of a Ca2+-ATPase from parotid membranes identified previously as an ecto-ATPase. The Ca 2+-ATPase of intact cells was insensitive to oligomycin (10 μg/ml), N-ethylmaleimide (NEM) (0.1 mM), ruthenium red (0.1 mM), sodium azide (1 mM), and was inhibited approximately 22% by sodium orthovanadate (Na3VO4) (1 mM). This profile was similar to the Ca2+-ATPase of intact cells. Trifluoperazine (TFP) (0.1 m M) inhibited the enzyme in intact cells by approximately 32%. The nucleotide substrate specificity of the enzyme also reflected very closely the pattern seen in isolated membranes.
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