Effects of ethanol on urinary acidification and on gluconeogenesis by isolated renal tubules

Abstract

Class I alcohol dehydrogenase (ADH) is present in the kidney of rats. Rats fed an alcohol-containing diet long-term had higher urinary pH and reduced titratable acidity compared with pair-fed controls; rates of ammonium excretion were unchanged. The effects of ethanol on the metabolism of isolated renal tubules were then studied. Gluconeogenesis from lactate, pyruvate, or glutamine was not inhibited by 10 mmol/L ethanol during 30- or 60-minute incubations, although there was a trend toward increased lactate/pyruvate ratios at 30 minutes in the presence of ethanol. When the medium was also supplemented with oleate, glucose synthesis from most substrates was decreased, and the addition of ethanol inhibited glucose synthesis dramatically. This interaction between oleate and ethanol was not abolished by 4-methylpyrazole, an inhibitor of ADH. This effect of ethanol was highly dependent on the concentration of oleate present in the medium and was not observed with palmitate or decanoate; the inhibition was reversed by increasing the medium concentration of albumin. We conclude that ethanol may mildly perturb the redox state of isolated kidney tubules without inhibiting glucose synthesis, and that ethanol and oleate interact to inhibit renal gluconeogenesis by a mechanism highly dependent on the fatty acid concentration. The mechanism by which ethanol in the diet reduces renal acid excretion remains unknown.