Histamine uptake and metabolism in intact isolated parietal cells

3H-Histamine binding, uptake and metabolism were investigated in intact isolated and enriched parietal cells from the dog and guinea pig. Histamine uptake was sodium dependent and followed by intracellular metabolism. The only metabolite that was detected and extracted from cytosol has been identified by TLC to N tau-methylhistamine. The histamine N-methyltransferase activity appeared to be sodium dependent and was inhibited by mepyramine and chlorpromazine, and also by higher concentrations (10(-4)--10(-3) mol/l) of cimetidine. Two blockers of the sodium channel, amiloride an aminoguanidine, also reduced the enzyme activity by an as yet unknown mechanism.