A defect in platelet aggregation in Bartter's syndrome.

A defect in both the first and second phase of platelet aggregation was found in four subjects with Bartter's syndrome, although template bleeding times were normal. The platelet abnormality was exacerbated by restriction of dietary sodium and lessened by the administration of inhibitors of prostaglandin synthesis. The aggregation defect was not found in other hypokalemic patients or in sodium-restricted normal control subjects. Platelet rich plasma from the subjects with Bartter's syndrome had an abnormally high content of cyclic adenosine 5'-monophosphate (AMP), which may have been responsible for the disordered platelet function. Plasma of these subjects induced both the high content of cyclic AMP and the aggregation defect in normal platelets, whereas suspension of the subjects' platelets in normal plasma improved their aggregation. These findings describe a unique defect of platelet aggregation in Bartter's syndrome, which may be associated with the altered prostaglandin metabolism found in this condition.