1. Blood alanine was measured in six patients undergoing total hip replacement and in four normal subjects starved for 4 days. Hypoalaninaemia occurred in both groups and persisted in the surgical patients despite an adequate diet. The blood alanine was also low in four insulin-dependent diabetic patients and in four patients with muscular dystrophy; it was normal in four patients with cirrhotic liver disease.
2. The removal of an intravenous l-alanine load (12 g; 133 mmol) was significantly increased after surgery and in the diabetic patients, unaltered by starvation, and decreased in the cirrhotic patients.
3. Increases in blood glucose were observed when alanine infusion was performed 6 h after surgery and after 3 days' starvation. Increases in blood lactate and pyruvate always occurred after alanine infusion but were most marked 6 h after surgery.
4. These results show that the metabolic response to an alanine load and the ability of the body to remove it alter with change in physiological state, and that the hypoalaninaemia after surgery and in diabetes is related to an increased removal of intravenous alanine, whereas that during starvation is not.