Body sodium blood volume state in essential hypertension: abnormal relation of exchangeable sodium to age and blood pressure in male patients.

The circulatory volume and exchangeable sodium (NaE) were measured by the Berne group in 110 normal subjects and 12 patients with benign untreated essential hypertension. Total plasma volume (PV) and blood volume (BV) correlated with total NaE (r = 0.64-0.75, p less than 0.001); these correlations were similar in normal and hypertensive subjects. PV, BV, and NaE related to body surface area averaged normal in the hypertensive population. PV and BV were unrelated to age or blood pressure in both normal and hypertensive subjects; NaE correlated positively with age (r = 0.25, p less than 0.02) and arterial pressure (r = 0.25, p less than 0.02) in essential hypertensive but not in normal subjects. These relationships in essential hypertension confirmed a previous observation by the Glasgow group. Moreover, a combined analysis of both study populations, with a total of 211 hypertensive patients, revealed significant correlations between NaE and age (r = 0.38, p less than 0.001) or arterial pressure (r = 0.40, p less than 0.001) in male but not in female subjects. The NaE was significantly decreased in hypertensive males less than 35 years old as compared with appropriate controls (95.8 +/- 5.1 vs 99.1 +/- 6.5%, p less than 0.02). BV and body sodium content are on average normal in patients with benign essential hypertension. The NaE may even be decreased in young male patients. These observations do not support the concept that body sodium and fluid volume expansion represent the initial event leading to high blood pressure in patients with essential hypertension.