Age-dependent effect of ouabain on renal Na+,K+-ATPase

This study examines the effect of chronic ouabain-treatment on renal Na(+) handling in 12-week and 52-week old rats.

Wistar Kyoto rats aged 5 weeks or 45 weeks were treated with ouabain or vehicle during 7 weeks. Blood pressure was measured in conscious animals throughout the study. After 7 weeks of treatment urinary electrolyte concentration, Na(+),K(+)-ATPase activity and α(1)-subunit expression were determined in 12-week and 52-week old rats.

In 12-week and 52-week old rats ouabain produced a significant increase in systolic blood pressure. Although no differences were observed in Na(+) excretion in these animals, 12-week old ouabain-treated rats had lower Na(+),K(+)-ATPase activity in proximal tubules. However, 12-week old ouabain-treated rats had decreased fractional excretion of Na(+). In proximal tubules of 52-week old rats Na(+),K(+)-ATPase activity did not differ between vehicle and ouabain-treated groups.

Our results show that in Wistar Kyoto rats renal response to ouabain treatment may be age-dependent and that the hypertensive effect of ouabain is independent of the effect on renal Na(+),K(+)-ATPase.