title: p-Aminohippurate transport in canine tracheal epithelium.
abstract: The unidirectional fluxes of 20, 100, 500, and 2,000 microM rho-aminohippurate (PAH) were measured under open- and short-circuit conditions in canine tracheal epithelium mounted as flat sheets in Ussing chambers. In tissues pretreated with mucosal indomethacin (10(-6) M) and amiloride (10(-4) M), unidirectional PAH fluxes under short-circuit conditions increased with increasing bath concentrations but there was no significant net PAH transport. After stimulation of chloride secretion by mucosal cyclic adenosine 3',5' -cyclic monophosphate (cAMP 10(-3) M), there was a significant increase in the secretory flux of PAH and a significant decrease in the absorptive flux of PAH. This resulted in net PAH secretion that demonstrated saturation kinetics with an apparent Michaelis-Menten constant of 754 microM by Lineweaver-Burk analysis. Intracellular concentrations of PAH were 0.4-1.2 times bath concentrations after pretreatment with indomethacin and amiloride and increased to 2.6-3.3 times bath concentrations after cAMP. Under open-circuit conditions, secretory PAH flux decreased and absorptive flux increased resulting in net PAH absorption. We conclude from these early studies that the canine tracheal epithelium possesses a specialized system for the transport of organic anions in the airways and that this transport system may share many similarities with organic anion transport in the kidney.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000618:Aminohippuric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D004285:Dogs; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D014132:Trachea / Q000378:metabolism*; D010130:p-Aminohippuric Acid / Q000378:metabolism*
chemical_list: D000618:Aminohippuric Acids; D003994:Bucladesine; D000584:Amiloride; D000242:Cyclic AMP; D007213:Indomethacin; D010130:p-Aminohippuric Acid