Effects of TMB-8, a calcium antagonist, on transport properties of the isolated canine tracheal epithelium

Abstract

The effects of the putative intracellular Ca 2+ antagonist, TMB-8 (8- N, N-diethylamino)-octyl-3,4,5-trimethoxybenzoate), on the canine tracheal epithelium were examined. Luminal addition reduced rapidly, but reversibly, the transmucosal potential difference and increased the resistance across the open-circuited epithelium. Under short-circuit conditions, the drug reduced stimulation by prostaglandin E 2, forskolin, 8-bromo cyclic AMP, prostaglandin F 2α and A23187. Inhibition of prostaglandin E 2 responses were accompanied by reversal of net Cl − fluxes produced by the agonist. The effect of TMB-8 were unaffected by increasing Ca 2+ in the bathing solutions, and were not mimicked by procaine, nitrendipine, calmidazolium, compound 48 80 or trifluoperazine. W7 did, do a limited extent, produce similar responses, though the drug was more toxic, and the effects were irreversible.