The effects of insulin on urinary urea and ammonia production

15N-labelled glycine, ammonium chloride, and L-aspartic acid were infused intravenously into a series of non-diabetic adults at a constant rate for 4 to 8 hours. Midway during the infusion, a pulse of 8-10 units of regular insulin was injected as a pulse or infused at a constant rate for the remainder of the 15N infusion period. Frequent urine specimens were collected during the infusion period. The 15N enrichment of the urinary urea, ammonia, and amino acids increased smoothly with time until the insulin was given. The pulse of insuline caused a downturn on the N enrichment. We concluded from this that a) the effect of a pulse of insulin on human urea and ammonia metabolism lasted for about one hour; and b) insulin affected glutamine distribution in the plasma.