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Whole body protein turnover was measured in 11 patients before and after elective orthopaedic operations be giving 15N-glycine orally every 4 hours for 32 hours. The patients were maintained throughout on a constant protein intake. In 2 control subjects a comparison was made between intermittent dosage and continuous infusion of 15N-glycine for the estimation of total protein turnover. With intermittent dosage the 15N abundance in urinary urea reached a constant level after about 24 hours. Rates of total protein synthesis and breakdown were calculated from the 15N abundance at the plateau level. After surgery there was a moderate increase in urinary N output. The apparent N balance (intake--urinary N) was -0-52 +/- 1-31 g/d (mean +/- s.d.) before operation and -7-51 +/- 4-5 g/d after operation. The rate of protein synthesis fell from 3-83 +/- 0-73 g kg-1 d-1 before operation to 2-94 +/- 0-83 g kg-1 d-1 after operation. This difference is statistically significant (0-05 greater than P greater than 0-01). There was no significant change in the rate of protein breakdown. The possibility remains that a block in protein synthesis, probably mainly in muscle, may be partly responsible for the so-called 'catabolic' loss of nitrogen after injury, but this has not been proved.

Insulin absorption from the human intestine without the necessity of suppressing the activity of pancreatic enzymes has been demonstrated in an adult male subject who survived total pancreatectomy. Following a large dose of insulin the fraction absorbed was small and the reason for this is discussed.