Sodium/potassium-adenosine triphosphatase on erythrocyte ghosts from pregnant women and its relationship to pregnancy-induced hypertension.

The regulation of electrolytes has been proposed as a possible determinant in hypertensive conditions, including pregnancy-induced hypertension. We report a study of sodium/potassium-adenosine triphosphatase in erythrocyte membranes of 59 patients with pregnancy-induced hypertension and 48 normotensive pregnant controls. The kinetics of the enzyme were also investigated, and the enzyme activity related to different degrees of pathology. A marked reduction of the enzyme activity was found in hypertensive patients, compared with controls. This reduction was greater when hypertension was associated with worse prognostic signs, such as proteinuria. These features are in agreement with the increased sodium content and the increased vascular reactivity found in pregnancy-induced hypertension. The enzyme activity appears to be decreased by means of a conformational modification of the enzyme sites, a phenomenon related to the hypertensive condition.