Histamine-induced decrease of membrane-bound calcium ions in the membrane fraction of rabbit taenia coli.

The difference between the interactions of acetylcholine and those of histamine with membrane-bound Ca2+ was studied. Plasma membrane vesicles were prepared from two types of smooth muscle of rabbit intestine: one sensitive to histamine and the other insensitive. The membrane vesicles were incubated with Ca2+ and bound Ca2+ was measured fluorometrically with chlorotetracycline. Acetylcholine did not affect the fluorescence, whereas histamine decreased it in preparations sensitive to histamine but not in those insensitive to histamine.