Potentiation by sulphydryl agents of the responses of guinea-pig isolated ileum to various agonists.

Sulphydryl agents (dithiothreitol, mercaptoethanol, monothioglycerol, cysteine, glutathione) increase non-specifically the potency of various agonists (acetylcholine, 5-hydroxytryptamine, nicotine, bradykinin, prostaglandin E2) on the guinea-pig ileum. These effects are of non-cholinergic origin and are not related to prostaglandin synthesis. Sulphydryl agents act directly on the smooth muscle cells of the guinea-pig ileum most probably by reducing disulphide bonds located on the membrane surface and by this mechanism modulate the muscular contractile activity.