Ouabain induced hypertension and Na + ,K + ‐ATPase in Wistar rats

Abstract

This study examined the effects of ouabain treatment in Na+,K+-ATPase (NKA) activity and expression in rat renal proximal tubules and intestinal mucosa. At 5 weeks of age pellets of ouabain or placebo were implanted. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were recorded during 7 weeks and NKA activity and α1-NKA subunit expression were determined. Three weeks after pellet implantation ouabain treated rats developed hypertension. SBP and DBP values (in mm Hg) in ouabain-treated rats were significantly different from placebo-treated animals (ouabain, 141±2 and 98±1; placebo, 119±1 and 88±2, respectively). There were no differences in HR and bodyweight between treatments. SBP and DBP values increased until the 5th week of treatment (ouabain, 156±3 and 115±5; placebo, 126±3 and 95±4, respectively). In renal proximal tubules of ouabain-treated rats NKA activity and α1-NKA subunit expression were decreased by 22.6% and 51.4%, respectively. In the intestinal mucosa of ouabain-treated rats there was a 31.8% decrease in NKA activity in jejunum, but not in the ileum or proximal colon. The expression of α1-NKA subunit in jejunum and ileum was not affected by ouabain treatment. These results suggest that changes in NKA activity induced by chronic ouabain treatment are tissue specific and may account for development of hypertension. Supported by grant POCI/SAU-FCF/59207/2004