Decreased platelet vitamin C in diabetes mellitus: Possible role in hyperaggregation

To determine whether the handling of Vitamin C in the diabetic might be altered and might relate to the increased platelet sensitivity, we have investigated levels of platelet Vitamin C in the diabetic and determined the effects of Vitamin C or on platelet aggregation.

Levels of ascorbic acid, as tested by a lingual method, were significantly lower in diabetics than in normals (p < . 01). Ascorbic acid levels in washed platelets from diabetics were significantly lower than from normals (45. 2±3 μg/10¹⁰ platelets vs. 25. 5±2 μg/10¹⁰ platelets, p < . 001). The effects of ascorbic acid on platelet aggregation were studied by adding ascorbic acid in buffered solution (pH 7. 35) prior to aggregating agents. Ascorbic acid (1000 μg/ml) in platelet-rich plasma consistently inhibited platelet aggregation with threshold concentrations of ADP, epinephrine, and collagen, but enhanced aggregation with arachidonic acid. With washed platelets, ascorbic acid inhibited arachidonic acid-induced aggregation. To rule out an interaction of ascorbi acid and arachidonic acid in the medium, platelets were incubated at 37°C for 10 minutes with varying concentrations of ascorbic acid, rewashed, and aggregation with arachidonic acid tested. Aggregation was inhibited in a linear dose-dependent fashion. Oral ingestion of ascorbic acid (2 gm/day) for seven days by normal non-smoking males produced a marked inhibition of aggregation. In a similar study, platelets from an insulin-dependent diabetic showed no change in aggregation. These results suggest that platelet levels of ascorbic acid may relate to the hyper-aggregation of platelets from diabetics.