Cellulose acetate, starch gel, and immunoelectrophoresis of human serum “albumin” extracts were performed. TCA/ethanol extraction altered the albumin so that polymers were present in addition to normal monomer albumin. Alpha1globulin was also present in the extracts, proving them to be heterogeneous in nature.
Nevertheless, extracts from nondiabetic and diabetic sera demonstrated insulin antagonism when measured on rat hemidiaphragms in physiologic serum concentration (4.0 per cent). Reduced concentration (1.25 per cent) of diabetic extracts still demonstrated insulin antagonism; normal extracts did not. These results, consistently found, support the idea that a difference exists between nondiabetic and diabetic humans in quantity of insulin antagonist associated with circulating protein. Extracts of the same blood sample, or of blood from the same subject on different days, gave reproducible results from one observation to another.
Despite constancy of insulin concentration in hemi-diaphragm preparations, biologic effect of insulin (glucose uptake increase) varied. At all levels of insulin effect diabetic extracts significantly antagonized insulin compared to nondiabetic extracts. To show differences in effect among individual extracts, comparison was made between per cent change from basal uptake produced by extract-plus-insulin and that produced by insulin alone. In twenty-seven of thirty-three nondiabetic subjects (82 per cent) change in glucose uptake produced by insulin-plus-extract was over 60 per cent of that produced by insulin alone; in six (18 per cent) the change lay between 50 per cent and 60 per cent. In all thirty-nine diabetic subjects change from basal uptake was less than 60 per cent of that produced by insulin alone.