Phasic vascular sodium pump changes in deoxycorticosterone-hypertensive rats

We determined the sodium pump activity, measured as ouabain-sensitive 86Rb+ uptake, in the tail arteries of rats treated with deoxycorticosterone and sodium chloride for 6, 9, 14, 28, and 50 days. Systolic blood pressures, plasma sodium, potassium, and creatinine concentrations were measured, and the body weights were recorded. Vascular sodium pump activity was suppressed (by 27%) at the 6th day of deoxycorticosterone and sodium chloride treatment, a prehypertensive state. By the 9th day, blood pressure of deoxycorticosterone-treated and sodium chloride rats had increased, but sodium pump activity was not different from that of control animals. However, increases in sodium pump activity were noted after 14 and 28 days of deoxycorticosterone and sodium chloride treatment (18 and 21%, respectively). By 28 days, a fully developed hypertension was noted. At 50 days, rats displayed lower vascular sodium pump activity (by 23%) than the controls. These rats, although hypertensive, had significantly lower systolic blood pressures than the rats treated for 28 days. They had high plasma creatinine levels, low potassium and sodium concentrations, and low body weights compared to the controls, suggesting the presence of a malignant state. Our data indicate that there are time-related changes in the vascular sodium pump activity with this type of hypertension.