Increased Sodium Permeability and Transport as Primary Events in the Hypertensive Response to Deoxycorticosterone Acetate (DOCA) in the Rat

We report here that 18-24 h after subcutaneous administration of DOCA to the rat, plasma [Na] was significantly increased and [K] reduced without change in cell Na concentration, [Na]i, or cell K concentration, [K]i, as measured in rapidly excised tail arteries. The large increase in the transmembrane K gradient, operationally [K]i/[K]o, was associated with a significant decline of about 7 mV in the transmembrane membrane potential (Em) measured in small mesenteric arteries in situ, and a small but significant rise in blood pressure. We conclude that the permeability of the membrane to Na relative to K was increased at this time but enhanced transport of both ions was sufficient to maintain near-normal cell concentrations. These were primary events in relation to the hypertension induced by DOCA, as the rise in plasma [Na] and fall in [K] were already apparent at 6 h.