Non-hypertensive men with a positive family history of hypertension in two generations (N = 16) were compared with weight-matched (N = 13) and lean (N = 12) control groups with a negative family history of hypertension with respect to the activity of the renin-angiotensin-aldosterone system at baseline and during an oral glucose tolerance test. Blood pressure was measured phonographically after 30 min of semirecumbent rest and the oral glucose tolerance test was performed after a 10-h overnight fast with 100 g of glucose given orally. Blood samples were drawn from a peripheral catheter at baseline, 30 and 120 min after the glucose challenge. Systolic and diastolic blood pressures did not differ between subjects with a positive or a negative family history of hypertension. At baseline, blood glucose and plasma insulin were similar in the three groups while the group with a positive family history of hypertension had a significantly lower plasma renin activity (PRA) (0.85 +/- 0.09 compared with the weight-matched but not with the lean control group (1.36 +/- 0.13 and 1.06 +/- 0.15 ng AI.ml-1.h-1; p < 0.01 and NS, respectively). The PRA increased significantly after the glucose challenge in all groups (p < 0.01), while the plasma aldosterone concentration decreased after 30 min and then showed an increase at 120 min. The PRA response was less pronounced in the group with a positive family history of hypertension compared with the weight-matched and lean control groups (p < 0.05 and p < 0.01, respectively). Serum potassium did not change significantly in either group after the glucose challenge. Urinary sodium excretion was similar in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)