[Total blood volume in essential and secondary hypertension].

To study the role of volume factors in the pathogenesis of hypertension, total blood volume (TBV) was determined in 43 patients with essential hypertension, 10 with primary aldosteronism, 5 with Cushing's syndrome, 5 with renovascular hypertension and 23 age-matched normotensives. The radioisotope (131I) labeled plasma tracer technique was employed under conditions of constant sodium intake (200mEq/day). The TBV values obtained were expressed as % normal against the predicted values according to the formulae of Fujita and his co-workers. The results were as follows: (1) TBV was increased in patients with primary aldosteronism. (2) In essential hypertensive patients, with either normal or low plasma renin activity, TBV was normal. (3) There was no increment of TBV in patients with Cushing's syndrome. These results suggest that expanded intravascular volume plays a major role in the mechanism of hypertension with suppressed plasma renin activity in primary aldosteronism, whereas other unknown factors may be related to the causes of hypertension in patients with essential hypertension and Cushing's syndrome.