POLARIZED EFFECTS OF AMILORIDE AND 4,4'-DIISOTHIOCYANO-STILBENE-2,2'-DISULFONIC ACID ON ATP-INDUCED CONTRACTION OF TRACHEA

Polarity in the effects of amiloride and 4,4'-diisothiocyano-stilbene- 2,2'-disulfonic acid (DIDS) in the guinea-pig isolated, perfused trach ea was investigated to evaluate the roles of epithelial and airway smo oth muscle Na+ and Cl- channels in the development of contractile resp onses to ATP. The blockers were applied to the mucosal (intraluminal) perfusing solution or to the serosal (extraluminal) bath before the se cond of two challenges with ATP (10(-4) M), which was added to the sam e bath as the blocker, or to the abluminal bath. In epithelium-intact tracheas, amiloride (10(-4) M) added to the extraluminal or intralumin al bath rapidly (1 min) and extensively inhibited contractions to extr aluminally applied ATP (10(-4) M). In contrast, contractions to intral uminally applied ATP (10(-4) M) were relatively resistant to extralumi nal and intraluminal amiloride (10(-4) M), in terms of the degree and onset of the inhibition. DIDS (10(-4) M) present in the extraluminal o r intraluminal baths caused a slowly developing elevation of baseline tone. After a 30 min incubation, extraluminal DIDS potentiated respons es to extraluminally added ATP, but intraluminal DIDS inhibited contra ctions to ATP added to the extraluminal and intraluminal baths. In con trast to the intact tracheas where there was no difference, the second response of epithelium-denuded preparations to intraluminally adminis tered ATP was diminished. In rubbed tracheas the response to intralumi nally added ATP was inhibited further by intraluminal amiloride but wa s potentiated by intraluminal DIDS. The results suggest that the effec ts of amiloride and DIDS were polarized across the tracheal wall and i nvolved epithelial and smooth muscle ion channels.