The effects of insulin on urinary urea and ammonia production

¹⁵N-Iabelled 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 the¹⁵N infusion period. Frequent urine specimens were collected during the infusion period. The¹⁵N enrichment of the urinary urea, ammonia, and amino acids increased smoothly with time until the insulin was given. The pulse of insulin caused a downturn on the¹⁵N 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.