Operational modes of the organic anion exchanger in canine renal brush-border membrane vesicles.
This study delineates the various operational modes catalyzed by the organic anion exchanger present in the canine renal brush-border membrane. The experiments examined the carrier-mediated effects of various organic and inorganic anions on the transport of either p-[3H]aminohippuric acid ([3H]PAH) or 36Cl-. [3H]PAH countertransport was significantly stimulated by PAH, urate, Cl-, Br-, HCO3-, and by a pH gradient. This pH stimulation remained in the absence of HCO3- (i.e., under N2), implying PAH-OH- exchange. Furosemide, bumetanide, penicillin, and probenecid inhibited countertransport of [3H]PAH. Likewise, the above anions produced cis inhibition of [3H]PAH transport. The cis and trans effects of SO4(-2) and formate were minimal. 36Cl- countertransport was stimulated by PAH, Cl-, Br-, HCO3-, formate, and by a pH gradient that was effective even in the absence of HCO3- (i.e., under N2), implying Cl- -OH- exchange. Cl- -OH- and Cl- -Cl- exchange was inhibited by PAH. In each instance, the trans-stimulation of 36Cl- efflux was insensitive to maneuvers that created an inside-positive membrane potential, demonstrating electroneutral mediated exchange. We conclude that the organic anion transporter can operate in three distinct exchange modes: organic-organic, organic-inorganic, and inorganic-inorganic.
Steffens
T G
TG
Department of Pharmacology, State University of New York Health Science Center, Syracuse 13210.
Holohan
P D
PD
Ross
C R
CR
D000818:Animals; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D004285:Dogs; D007473:Ion Channels / Q000378:metabolism; D007474:Ion Exchange; D007668:Kidney / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D010130:p-Aminohippuric Acid / Q000378:metabolism
D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D007473:Ion Channels; D008565:Membrane Proteins; D010130:p-Aminohippuric Acid