Effect of chronic acid loading on rat renal basolateral membrane bicarbonate transport.
The effect of chronic acid loading on the activity of luminal membrane Na(+)-H+ exchange and basolateral membrane Na+/HCO3- cotransport and Cl(-)-HCO3- exchange was investigated using membrane vesicles isolated from rat renal cortex. Na(+)-H exchange activity was increased approx. 50% in brush-border membranes isolated from acidemic compared to control kidneys. Na+/HCO3- cotransport and Cl(-)-HCO3- exchange activity was increased approx. 45% and 100%, respectively, in basolateral membranes isolated from acidemic kidneys. The increased Na+/HCO3- cotransport activity resulted from an increased apparent maximal rate of transport (Vmax) with no change in affinity (Km) for Na+. In contrast to acid/base transport activities chronic acid loading had no effect on the activity of basolateral membrane Na+/dicarboxylate cotransport. These results suggest proximal tubule cells coordinately increased luminal and basolateral membrane acid/base transport activities to accommodate an adaptive increase in the capacity for transcellular bicarbonate reabsorption.
Grassl
S M
SM
Department of Pharmacology, State University of New York, Syracuse 13210.
D000818:Animals; D001692:Biological Transport; D002255:Carbonic Acid / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D028021:Sodium-Potassium-Chloride Symporters; D002255:Carbonic Acid; D012964:Sodium