Arachidonic acid uptake activity was measured in platelets obtained from 27 Type 2 diabetic patients and 18 age-matched control subjects. In both groups after 1 h incubation almost all the incorporated 14C-arachidonic acid was located in the phospholipids of the platelets. Arachidonic acid was predominantly incorporated into phosphatidylcholine. The radioactivity incorporated into platelets increased linearly with incubation time, up to 90 min. The linear increase was observed at arachidonic acid concentrations of 0.1-1.0 micrograms/ml in both groups. The rate of incorporation of radioactivity in diabetic platelets was about 1.4 times higher than that in control platelets at all arachidonic acid concentrations studied. The arachidonic acid uptake activity of diabetic platelets (577 +/- 26 ng/60 min per 10(9) platelets) was significantly higher than that in control platelets (410 +/- 26 ng/60 min per 10(9) platelets). No significant correlations were found between the arachidonic acid uptake activity and fasting plasma glucose, total cholesterol or triglyceride levels. The arachidonic acid uptake activity of platelets was significantly higher in diabetic patients with proliferative retinopathy than in those with little or no background retinopathy. In addition, there were no significant differences between control and diabetic subjects in the uptake activity of platelets for linoleic acid and oleic acid. These data may explain the elevated arachidonic acid content in diabetic platelet phospholipids and enhancement of thromboxane synthesis in diabetes.