Renal handling of electrolytes and (Na + K)-ATPase activity after unilateral nephrectomy during long-term ethanol feeding.

The effect of long-term ethanol feeding on the activity of (Na + K)-ATPase in cortex and outer medulla and fractional excretion of electrolytes in remnant kidney of adult rats after unilateral nephrectomy were studied. Wistar adult rats were fed 20% (v/v) aqueous ethanol solution as sole drinking fluid for 8-10 weeks. Right kidney was removed under ether anaesthesia. The animals were subjected to an acute NaCl loading by means of a continuous infusion given 2, 7 and 14 days after nephrectomy. Renal handling of electrolytes was estimated from fractional excretion of sodium and potassium. After the infusion the animals were killed and (Na + K)-ATPase and Mg2+-ATPase activities were measured in the cortex and outer medulla of the remnant kidney. Two days after nephrectomy both groups showed a gradual increase of renal (Na + K)-ATPase activity reaching 60 percent at day 14. Mg2+-ATPase activity did not change with respect to basal values. Compared to basal values the fractional excretion of sodium after nephrectomy, dropped in both groups but more significantly in the ethanol-fed rats than in the control group. Fractional excretion of potassium did not change in the control group after nephrectomy while the ethanol-fed group displayed a significative decrease at days 7 and 14. According to our results the rise in renal (Na + K)-ATPase activity is consistent with the renal sodium retention found in ethanol-fed rats.