Changes in vascular ionic composition at different stages of DOC-salt hypertension in the rat.

1. Sequential changes in the ionic composition of the aorta and skeletal muscle were followed during 1, 2 and 4-6 weeks in 30 rats given deoxycorticosterone (DOC) and salt supplemented with potassium chloride. Twenty-one rats, drinking water, were used as controls. 2. Twenty-five per cent of the test rats were hypertensive after 1 week, 60% after 2 weeks and 100% after 4-6 weeks. 3. Muscle potassium fell in all test rats by an average of 15%. In contrast, aortic potassium fell by 19% only in those rats which did not develop hypertension after 1 week. 4. Total and non-inulin sodium and water of the aorta were normal in rats which remained normotensive after 1 or 2 weeks and high in those which became hypertensive during the same period. 5. Total sodium and water content of the aorta were also high in rats which were hypertensive at 4-6 weeks. However, because of simultaneous expansion of the inulin space, non-inulin fractions were normal in this group. 6. Results suggest that vascular ionic changes participate in the pathogenesis of DOC-salt hypertension through more than a single mechanism.