ions regulate activity of [Na.sup.+],[Cl.sup.-](HC[O.sup.-.sub.3])-ATPase in the Mucosa of rabbit small intestine

We studied the effects of bivalent metal ions on activity of [Na.sup.+],[Cl.sup.-](HC[O.sup.-.sub.3])-ATPase was studied. In contrast to [Ba.sup.2+], [Co.sup.2+], [Zn.sup.2+], and [Mn.sup.2+] ions, [Ca.sup.2+] and [Mg.sup.2+] ions in a concentration of 0.25 mM completely inhibited this enzyme. Histamine in vivo significantly decreased the inhibiting effect of [Ca.sup.2+] on [Na.sup.+],[Cl.sup.-](HC[O.sup.-.sub.3])-ATPase. A possible mechanism of regulation of enzyme activity by [Ca.sup.2+] ions and its possible relation with CFTR protein providing permeability of enterocyte apical membrane for [Cl.sup.-] ions was proposed. Key Words: secretory process; small intestine; transport ATPase; CFTR