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

Aims: This study examines the effect of chronic ouabain-treatment on renal Na+ handling in 12-week and 52-week old rats. Main methods: 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 alpha(1)-subunit expression were determined in 12-week and 52-week old rats. Key findings: 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. Significance: 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. (C) 2011 Elsevier Inc. All rights reserved.