A circulating inhibitor of platelet aggregation in Bartter's syndrome.

Aggregation studies were performed on platelets from five patients with Bartter's syndrome. Epinephrine failed to induce aggregation in all five patients. Adenosine 5'-diphosphate (ADP) produced a single reversible phase of aggregation, and there was depressed sensitivity to collagen. Response to ristocetin was normal. There was a dose-related inhibition of ADP-induced platelet aggregation when plasma from the patients was addeded to normal platelet-rich plasma. This inhibition was diminished or absent when patients were receiving aspirin. Washed platelets from two patients who were no longer undergoing aspirin therapy, showed a normal response to epinephrine in normal platelet-poor plasma. Bleeding time was reduced from 23 minutes to 12 minutes in one patient while on aspirin therapy. These studies suggest that a circulating inhibitor of platelet aggregation, probably of prostaglandin origin, is present in the plasma of patients with Bartter's syndrome.