The relation of cellular sodium to the onset of hypertension induced by DOCA-saline in the rat.

Groups of 15 rats were injected subcutaneously with a microcrystalline suspension of DOCA and given 1% saline as drinking water for periods ranging from 2 to 16 days. The in vivo transmembrane distribution of Na and K in relation to blood pressure was assessed in terms of plasma [Na] and [K] measured with ion-specific electrodes; smooth muscle cell Na, K and water were measured in the rapidly excised tail artery. A small increase in blood pressure was observed in week 1 of treatment and was followed by an abrupt increase to higher levels at about day 10. Plasma [Na] was elevated and [K] lowered throughout in a new steady state with a reciprocal change of about 1 mmol/l. There were minor changes in intracellular [K] in rapidly excised fresh tail artery samples so that the transmembrane K gradient (EK) was at all times increased by greater than 10 mV, indicating enhanced Na-K transport. In general, intracellular [Na] was directly and Na gradient inversely related to blood pressure (P less than 0.01).