[Essential hypertension and diabetes]

Exchangeable sodium (E-Na), plasma volume (PV), and plasma renin activity (PRA) have been studied in 19 patients with essential hypertension and diabetes, and the results compared to those of non-diabetic patients with benign essential hypertension. None of the cases had renal disease or hypertension with systolic predominance. E-Na was 114 +/- 9.74 (SD), significantly superior to that of normal subjects (p less than 0.001). An elevated E-Na was observed in 52.6% of the diabetic group, while PV was normal. PRA levels were normal in most patients, mean 1.28 +/- 1.97 ng ml-1 h-1, only two patients disclosing an elevated PRA (10.5%). No relationship was found between PRA and age, blood pressure, and E-Na. From the comparison of results between diabetic and non-diabetic hypertension patients it appears that: 1) no differences between mean PRA and E-NA exist, although a greater percentage of diabetics have an elevated E-Na, and 2) in the non-diabetic group there is a positive correlation between E-NA and PV, while in the diabetic group such a correlation is negative (p less than 0.05). The finding of an elevated body sodium in patients with essential hypertension and diabetes probably represents a true abnormality in the body composition of these patients, although there is no explanation for the fact that it is unassociated to an increase of the plasma volume, as opposed to essential hypertension in non-diabetics.