This study describes the effect of endogenous insulin on free plasma amino acids. The secretion of insulin was provoked by means of a standard glucose tolerance test.
Four healthy males responded by a drop in the levels of all twenty-two plasma amino acids, which were measured. In four insulin-dependent diabetics the glucose tolerance experiment effected only slight decreases in nineteen of twenty-two amino acids. Ornithine and histidine decreased significantly, whereas phenylalanine increased.
The over-all result indicates that endogenous insulin reduces the levels of the majority, if not all, free plasma amino acids.