Simultaneous whole-body
protein breakdown (using 15N-glycine) and urinary
3-methylhistidine (3MH) excretion rates were determined in six hospitalized normal volunteers after 10 days of
starvation and a subsequent 10-day period of total parental nutrition (TPN). These data were contrasted to whole-body
protein breakdown and urinary 3MH excretion in ten depleted (14.8%
body weight loss) patients with benign intraabdominal disease studied in the basal (48 hours without nutrient intake) and intravenously refed states. The rates of whole-body
protein breakdown were significantly reduced from basal (brief fasting or
starvation) conditions in both normal volunteers (p less than 0.01) and depleted patients (p less than 0.01) during TPN. The rate of
protein catabolism normalized for
creatinine excretion in patients was higher than that observed in normal subjects during both basal (p less than 0.05) and
intravenous feeding conditions. Daily urinary 3MH excretion was reduced during
intravenous feeding in both starved normal volunteer (235 +/- 13 mumol/d to 197 +/- 9 mumol/d p less than 0.05) and in depleted patients (209 +/- 31 mumol/d to 140 +/- 35 mumol/d), and an apparent linear relationship between
protein breakdown and urinary 3MH, normalized for
creatinine excretion, was obtained in both volunteer and patient (r = 0.85) populations during fasting-refeeding. However, separate regression analysis of the
protein breakdown and 3MH responses of both volunteer and patient groups under conditions of fasting,
starvation, and refeeding revealed significant differences between volunteer and patient populations during intravenous refeeding (p less than 0.01). Further analysis of 3MH excretion in relationship to
nitrogen balance during refeeding suggests a complex relationship between urinary 3MH excretion and whole-body
protein metabolism that may be partly related to the degree of antecedent
malnutrition.