Partial purification and studies of the plasma co-factor that potentiates platelet aggregation in diabetes mellitus

A co-factor is present in the plasma of some diabetics that potentiates the degree of in vitro aggregation of normal platelets after ADP stimulus. This paper presents important changes in the analysis technique that utilize recently appreciated knowledge about platelet aggregation and that were needed to permit characterization of the co-factor. By this new technique, the plasma co-factor activity of 33 normal adults and 43 normal children was significantly lower (p less than 0.001) than that of the corresponding diabetic groups. Thirty-two percent of the adult and 23% of the child diabetics had an elevated plasma co-factor activity. None of the 71 diabetic children and only 12 of the 65 diabetic adults had severe retinopathy. These results correlate well with previous reports wherein the plasma co-factor activity was highest in patients who had severe retinopathy or nephropathy and was usually normal when microangiopathy was not evident. The co-factor was completely precipitated from the plasma of a diabetic with ammonium sulfate at the concentration of 34% of saturation. An aqueous solution of this precipitate retained co-factor activity during incubation at 56 degrees for 30 min but lost activity at neutral pH conditions. Co-factor activity eluted during gel filtration to indicate an estimated molecular weight of 21,000 daltons. The improved technique reported here should facilitate study of the platelet hyperaggregation co-factor and the pathophysiology of diabetic microangiopathy.