Aorta electrolytes of hypotensive potassium-deficient rats

Influence of dietary potassium and sodium/potassium molar ratios on the development of salt hypertension

Among genetically hypertension-prone rats, dietary sodium (chloride) was demonstrably hypertensinogenic and potassium (chloride) antihypertensinogenic. On diets containing the same NaCl but different KCl concentrations, mean blood pressure was greater in rats receiving less dietary potassium, i.e., diets with a higher Na/K molar ratio. On diets with different absolute concentrations of NaCl and KCl, but the same Na/K molar ratios, rats on the higher absolute NaCl intakes had the higher blood pressures. On diets with different absolute concentrations of NaCl and KCl, and different Na/K molar ratios, a group on a lower absolute NaCl intake but with a higher Na/K ratio could have more hypertension than a group on a higher absolute NaCl intake but with a lower Na/K ratio. At equivalent molar ratios, the respective effects of these two ions on blood pressure were dominated by that of sodium. It was concluded that the dietary Na/K molar ratio can be an important determinant for the severity, or even development, of salt-induced hypertension. The mechanism of the moderating effect of potassium on sodium-induced hypertension was unclear.

On the Mechanism of Antihypertensive Action of Hydrochlorothiazide in Rats

Hydrochlorothiazide significantly diminishes blood pressure in rats with DCA hypertension. Infusion with hypertonic saline or dextrose failed to reverse the blood pressure effects of hydrochlorothiazide. Infusion of hypotonic saline failed to restore blood pressure to the levels of hypertension in untreated controls in one experiment but tended to do so in another. There was no significant diminution of the inulin space accompanying the hypotensive action of hydrochlorothiazide, nor any relation between the expansion of the extracellular and cardiovascular volumes by various infusions and their effects on blood pressures of thiazide-treated rats. Plasma or extracellular fluid volume alteration was, therefore, not the primary action of hydrochlorothiazide in these rats. Analyses of the composition of plasma, aorta, stomach muscle, psoas muscle, or left ventricle did not support the theory that hydrochlorothiazide acts by decreasing the concentration of intracellular sodium or increasing the ratio of extracellular to intracellular sodium. Changes in composition of the left ventricle suggested that alterations in its function may have influenced some of the blood pressure changes noted. It is suggested that attention should be paid to the action of hydrochlorothiazide on other constituents in vascular and cardiac muscle.