Chloride removal selectively inhibits phasic contractions of guinea pig ileal longitudinal smooth muscle.

Removal of external chloride selectively and reversibly inhibits the phasic responses of the guinea pig ileal longitudinal muscle to high potassium and cholinergic stimulation. The binding of calcium to a relatively superficial pool is affected by chloride removal. Alterations in anionic composition of bathing solution affects the availability of calcium for excitation--contraction (E--C) coupling in smooth muscle.