AN ABNORMAL SODIUM-METABOLISM IN JAPANESE PATIENTS WITH ESSENTIAL-HYPERTENSION, JUDGED BY SERUM SODIUM DISTRIBUTION, RENAL-FUNCTION AND THERENIN-ALDOSTERONE SYSTEM

Objective The role of the renin-aldosterone system and the ability of renal sodium reabsorption to facilitate pressure natriuresis were anal yzed by using a sufficient number of Japanese patients with essential hypertension. Methods We studied 3222 normal Japanese subjects (610 in Kashiwa City Hospital and 2612 in Shinshu University Hospital), 741 J apanese patients with essential hypertension (256 in Kashiwa City Hosp ital and 485 in Shinshu University Hospital), 20 patients with aldoste rone-producing adenomas and 11 patients with idiopathic hyperaldostero nism to determine the possible roles of sodium, renal function, and pl asma aldosterone concentration (PAC) on blood pressure elevation. Inap propriate elevation of aldosterone levels [elevation of the aldosteron e:plasma renin activity (PRA) ratio] was used to assess aldosterone ac tion. Results The peak of the serum sodium distribution curve was appr oximately 2 mmol/l higher in the patients with essential hypertension than it was in controls. The prevalence of higher serum sodium concent rations (greater than or equal to 147 mmol/l) also was increased signi ficantly hypertensive patients, Age-related deterioration of renal fun ction did not explain the hypertension and abnormal sodium metabolism in the hypertensive patients. In stepwise regression analysis, the ser um sodium concentration was related inversely to the PRA and positivel y to the PAC:PRA ratio. Although there was an inverse relationship bet ween urinary sodium excretion (representing sodium intake) and the PRA , urinary sodium excretion proved not to be significant as a source of variation in the PAC or in the PAC:PRA ratio in the hypertensive pati ents. Although the PAC was within the normal range in patients with se rum sodium concentrations of 147 mmol/l or more and an elevated PAC:PR A ratio, it was inappropriately high for the stimulus applied, as indi cated by the PRA; this is similar to the situation with aldosterone-pr oducing adenomas or idiopathic hyperaldosteronism. Conclusion Serum so dium distribution patterns differed between normal subjects and patien ts with essential hypertension in this Japanese population. The deteri oration of renal function and increased sodium intake did not explain this abnormal sodium metabolism, A higher serum sodium concentration i s related to an elevated blood pressure, and, in some patients, an ina ppropriate elevation of plasma aldosterone levels, Of the Japanese hyp ertensive patients, 10-14% exhibited serum sodium concentrations of 14 7 mmol/l or more and inappropriate elevations of aldosterone level (su ppressed PRA and normal aldosterone level). The defect in these patien ts presumably lies in the inappropriately high secretion of aldosteron e.