Sodium-potassium cotransport in hypertension and hypotension.

Furosemide-sensitive Na-K cotransport was measured as zero-trans efflux of each ion from fresh or Na loaded erythrocytes in normotensives (n = 34), essential (n = 41) or secondary (n = 12) hypertensives and essential (n = 17) or secondary (n = 5) hypotensives. The stoichiometry of Na and K efflux was 0.9:1 in fresh cells and 1:1 in cells loaded with sufficient Na to give near the maximum velocity (Vmax) in a combined analysis. There was a tendency toward a negative correlation between the Vmax of Na efflux and serum total cholesterol (p = 0.09) in the whole and it was significant in normotensives (r = -0.60). Vmax of Na efflux also negatively correlated to age (p less than 0.01). After adjustment for age and total cholesterol level, essential hypertensives had a significantly (p less than 0.01) higher mean Vmax of Na efflux (0.657 +/- 0.029 mM/l cells/hr) than normotensives (0.388 +/- 0.045), while essential hypotensives had a lower value (0.212 +/- 0.047) (p less than 0.01). Na efflux from fresh cells adjusted for internal Na content was higher in essential hypertensives (0.173 +/- 0.018) than in normotensives (0.107 +/- 0.026) (p less than 0.05). Thus, elevated cotransport was linked to essential hypertension and reduced cotransport to hypotension. Whether it is a cause or a result remains to be further investigated.