Objective: To evaluate plasma atrial natriuretic factor (ANF) behavior in hypertensive patients with either insulin-dependent (type I) or non-insulin-dependent (type II) diabetes.

Research design and methods: Plasma ANF levels were measured in euglycemic normotensive patients (n = 18) and hypertensive patients (n = 18), in diabetic normotensive patients (type I diabetes, n = 12; type II diabetes, n = 12), and in diabetic hypertensive patients (type I diabetes, n = 12; type II diabetes, n = 22). In all groups, plasma ANF levels were determined at the end of a normal NaCl diet period (120 mmol NaCl per day for 10 days) in both the supine and the upright positions.

Results: Plasma ANF levels were significantly higher (P < 0.05) in hypertensive euglycemic patients (supine vs. upright: 13.4 +/- 6.7 vs. 8.5 +/- 4.3 fmol/ml) than in normotensive type I diabetic patients (supine vs. upright: 8.6 +/- 2.2 vs. 5.9 +/- 2.9 fmol/ml) but not in euglycemic normotensive subjects (supine vs. upright: 11.4 +/- 5.1 vs. 7.6 +/- 5.8 fmol/ml) and normotensive type II diabetic patients (supine vs. upright: 10.1 +/- 4.1 vs. 7.9 +/- 4.1 fmol/ml). Moreover, in the normotensive groups plasma ANF levels did not significantly differ among euglycemic type I and type II diabetic patients. However, the highest levels of plasma ANF were observed in hypertensive type II diabetic patients (supine vs. upright: 16.9 +/- 7.4 fmol/ml [P < 0.01 vs. euglycemic normotensive subjects, P < 0.0001 vs. normotensive type I diabetic patients, P < 0.01 vs. hypertensive type I diabetic patients and normotensive type II diabetic patients] vs. 11.6 +/- 2.9 fmol/ml [P < 0.005 vs. normotensive type I diabetic patients, P < 0.01 vs. hypertensive type I diabetic patients]). On the contrary, plasma ANF levels were higher (P < 0.05) in hypertensive type I diabetic patients (supine vs. upright: 10.8 +/- 1.9 vs. 6.4 +/- 2.2 fmol/ml) compared with normotensive type I diabetic patients, but not with any other patient group. A significant correlation between supine ANF and insulin levels was found in both type II diabetic (r = 0.457; P < 0.05) and nondiabetic hypertensive patients (r = 0.716; P < 0.0001).

Conclusions: These findings indicate that circulating ANF levels are markedly elevated in type II diabetic patients affected by essential hypertension. On the contrary, plasma ANF levels are in the range of normality in normotensive type I and type II diabetic patients.