title: Effects of harmaline on ion transport and oxygen consumption by the bovine tracheal epithelium.
abstract: The alkaloid harmaline is known to affect various membrane transport systems. This study examines the action of the drug on the short-circuit current (I0) and on the oxidative metabolism (Jr) in the tracheal epithelium of the cow. In this tissue I0 corresponds to the sum of two active transports: Na+ is absorbed and Cl- is secreted by a process based on the activity of the Na+ pump. A well defined relationship has been previously demonstrated between these active transports and the rate of O2 consumption (Schoenenweid et al., 1984 b). Low concentrations of harmaline (10(-6) to 5.10(-6) M) induced a small stimulation of I0. In contrast, larger concentrations (between 5.10(-5) and 10(-3) M) yielded a dose-related inhibition of I0, with an apparent concentration yielding 50% of maximal effect of 7.1.10(-4) M and maximal effect approaching 100%. The action was fully reversible after removal of the drug. The measurements of the fluxes of 22Na and 36Cl revealed that harmaline at a concentration of 8.10(-4) M, which decreased the I0 by 74 +/- 1% (n = 23), diminished both Na+ and Cl- transports, by 81 and 52%, respectively. The time course of I0 decay following the administration of harmaline was made of three components, with half-times of 0.34, 2.2 and 15.2 min. The time course was not appreciably modified when Cl- secretion was abolished with furosemide. Although harmaline, 10(-3)M, inhibited markedly I0, it did not modify Jr significantly. In contrast, when K+ in the incubation solution was omitted, both Ji and Jr were lowered.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002713:Chlorine / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006246:Harmaline / Q000494:pharmacology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors; D014132:Trachea / Q000378:metabolism*
chemical_list: D000470:Alkaloids; D007473:Ion Channels; D002713:Chlorine; D012964:Sodium; D006246:Harmaline