Myocardial Na,K-ATPase activity in rats with steroid and spontaneous hypertension

Vascular Na-K pump activity (ouabain-sensitive 86Rb uptake) and cardiac Na,K-ATPase activity are decreased in rats with one-kidney, one clip and reduced renal mass-saline hypertension. In the present study we measured left ventricular, microsomal Na,K-ATPase activity in rats with two steroid forms of hypertension; one-kidney, deoxycorticosterone acetate-saline (1-K, DOCA-saline) and one-kidney, dexamethasone (1-K, DEXA) hypertension and also in spontaneously hypertensive rats (SHR). Relative to one-kidney, normotensive (1-K, NT) control rats, cardiac Na,K-ATPase activity was decreased and Mg-ATPase activity was increased in rats with 1-K, DOCA-saline hypertension (systolic BP = 175 +/- 2 mmHg, sustained eight to 10 weeks, n = 11). The apparent dissociation constant of cardiac Na,K-ATPase for K was unchanged in these hypertensive rats. In rats with 1-K, DEXA hypertension (systolic BP = 171 +/- 1 mmHg, sustained eight to 10 weeks, n = 9), cardiac Na,K-ATPase activity was increased and Mg-ATPase activity was unchanged relative to 1-K, NT control rats. We observed no change in either cardiac Na,K-ATPase activity or Mg-ATPase activity in SHR (36-38 weeks of age, systolic BP = 186 +/- 7 mmHg, n = 12) relative to either age-matched normotensive Wistar-Kyoto or Wistar control rats. These studies therefore suggest that cardiac Na,K-ATPase activity is decreased in 1-K, DOCA-saline hypertensive rats, increased in 1-K, DEXA hypertensive rats and unchanged in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)