1. To investigate atrial natriuretic factor (ANF) and its relationship to the renin system in diabetes, we measured plasma immunoreactive ANF and plasma renin activity (PRA) in 27 non-ketotic diabetic patients without evidence of cardiac or overt renal disease, and compared them with 26 age- and sex-matched normal subjects.
2. Diabetic patients were divided prospectively into poor (PGC, n = 14) or moderate (MGC, n = 13) glycaemic control depending on their concurrent plasma glycohaemoglobin (HbA1) levels (> 9% or < 9%, respectively). Plasma ANF was elevated in PGC diabetic patients (15.7 ± 1.8 fmol/ml, mean ± sem) compared with MGC diabetics (9.9 ± 0.8 fmol/ml, P < 0.001) and normal subjects (10.1 ± 1.3 fmol/ml, P < 0.05).
3. In contrast, PRA was lower in the PGC diabetic patients (1.3 ± 0.3 pmol of angiotensin I h−1 ml−1) compared with the other groups (2.5 ± 0.5 and 2.1 ± 0.2 pmol of angiotensin I h−1 ml−1, P < 0.05). Diabetic groups had proportionally more patients with high prorenin values (over 30 ng h−1 ml−1) than the normal group, but there was no difference between the diabetic groups.
4. Among the diabetic patients, ANF was directly related to HbA1 (r = 0.49, P < 0.005) and urinary albumin excretion (r = 0.40, P < 0.02), and was inversely related to PRA (r = −0.36, P < 0.04) and plasma creatinine (r = −0.42, P < 0.02).
5. Systolic blood pressure was greater in PGC diabetic patients [133 ± 5 mmHg (17.7 ± 0.7 kPa)] than in MGC diabetic patients [117 ± 4 (15.6 ± 0.5 kPa), P < 0.05] and normal subjects [121 ± 3 (16.1 ± 0.4 kPa), P < 0.05]. Diastolic pressure was not significantly different among the groups.
6. The directionally opposite changes in plasma ANF and plasma renin in PGC diabetic patients may reflect a normal response to expansion of intravascular volume. It remains to be established whether these changes are factors in the early renal dysfunction of diabetes mellitus.