Effects of disodium cromoglycate on smooth muscle.

Recently, DSCG has been found to inhibit the contraction of guinea pig ileum smooth muscle, when induced by various pharmacologic stimuli. DSCG also seems to inhibit contractions induced by electrical stimuli when high and low frequencies are used. We intend to further clarify our understanding of the sites of action of DSCG by studying its effects on surgically-isolated guinea pig trachea and ileum. Tissue samples were bathed in Krebs solution and suspended at 37 degrees C with 95% O2 and 5% CO2 as proposed by Constantine. Some ileal samples were denervated by the method of Ambache. The isometric contractions of trachea and ileum were measured at basal conditions and after adding cumulative doses of nicotine, histamine, acetyl choline and PG-F2 alpha. The dose response curve for each substance was determined, as were the effects on each curve of DSCG. DSCG significantly inhibited nicotine-induced contractions of guinea pig ileum (nicotine stimulates the intestinal nerve plexus). Histamine and acetyl choline-induced contractions of denervated ileum were also inhibited by DSCG. Contractions of isolated guinea pig trachea secondary to Ach, Hi and PG-F1 alpha were also effectively antagonized. Our results suggest that DSCG acts at two levels to inhibit ileal contraction: at the neural level, namely at Auerbach's plexus, and directly upon the smooth muscle fiber. These effects probably depend on the membrane stabilizing capability of cromolym sodium, that not only involve the mast cell, but extend to intestinal and bronchial smooth muscle as well. The action of DSCG on smooth muscle and mast cells probably contribute to its efficacy in bronchial asthma and food allergy.