Substrate responses to acid-base alterations in dog renal proximal tubules.
Proximal tubules from dog kidney were incubated for 2-6 min with low concentrations of pyruvate, glutamine, and malate. When initial medium citrate was between 0 and 0.5 mM and alpha-ketoglutarate was between 0 and 0.1 mM, concentrations of these two substrates in tubules and media after incubation were lower with 10 than with 40 mM HCO3-. Malate levels in tubules and media changed in the opposite direction. CO2 formation from labeled citrate or alpha-ketoglutarate was greater at low than at high HCO3-. In tubules treated with digitonin to disrupt the cell membrane, differences in citrate and alpha-ketoglutarate concentrations in tubules at high and low HCO3- were eliminated. The effects of acid-base changes seen in intact tubules on malate levels and on the rate of oxidation of labeled citrate persisted after digitonin pretreatment. These results show that acute effects of acid-base changes on citrate, alpha-ketoglutarate, and malate levels observed in intact renal cortex can be reproduced in isolated tubules. They suggest that these changes are related to changes in levels of citrate and alpha-ketoglutarate in cytoplasm without corresponding changes within mitochondria.
Simpson
D P
DP
Department of Medicine, University of Wisconsin-Madison 53792.
McSherry
N
N
Scarbrough
E
E
Zweifel
K
K
D000136:Acid-Base Equilibrium; D000818:Animals; D000863:Antacids / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D002245:Carbon Dioxide / Q000378:metabolism; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D003470:Culture Media; D004072:Digitonin / Q000494:pharmacology; D004285:Dogs; D007656:Ketoglutaric Acids / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D000863:Antacids; D001639:Bicarbonates; D002951:Citrates; D003470:Culture Media; D007656:Ketoglutaric Acids; D002245:Carbon Dioxide; D019343:Citric Acid; D004072:Digitonin