Although hyperinsulinemia and decreased high density lipoprotein cholesterol concentration can occur in patients with hypertension, there is no information available concerning the dynamic state of high density lipoprotein metabolism. To address this issue, we quantified high density lipoprotein turnover in 12 patients with mild hypertension and 11 matched subjects with normal blood pressure. Patients with high blood pressure had lower high density lipoprotein cholesterol concentrations. Fractional catabolic rates of 125I-apolipoprotein AI (apoAI)/high density lipoprotein were faster in patients with hypertension (0.36 +/- 0.02 versus 0.26 +/- 0.02 l/day, p less than 0.001). Total synthetic rates of apoAI were also significantly greater in patients with high blood pressure (17.4 +/- 1.1 versus 13.2 +/- 0.6 mg/kg/day, p less than 0.001). Although significant correlation was observed between blood pressure and fractional catabolic rate of 125I-apoAI/high density lipoprotein in the experimental population (r = 0.52, p less than 0.01), no relation was found when patients with normal blood pressure or hypertension were considered separately. However, a highly significant positive correlation was found between 125I-apoAI/high density lipoprotein fractional catabolic rate and insulin concentration in the entire population (r = 0.72, p less than 0.001). In conclusion, the patients with mild hypertension studied were hyperinsulinemic, had a faster fractional catabolic rate of 125I-apoAI/high density lipoprotein, and a lower high density lipoprotein-cholesterol concentration. It is suggested that the changes seen in high density lipoprotein-cholesterol concentration and 125I-apoAI/high density lipoprotein fractional catabolic rates were secondary to the hyperinsulinemia and not due to the high blood pressure per se.