Proline metabolism in adult male burned patients and healthy control subjects.

Postabsorptive proline flux, oxidation, and endogenous biosynthesis were determined in five severely burned intensive-care-unit patients (mean age 27 y) and in six healthy, young-adult control subjects. Continuous primed, intravenous, 160-min, dual stable-isotope-tracer infusions of L-[1-13C]proline and L-[methyl-2H3]leucine were used in conjunction with measurement of plasma proline concentration and 24-h urinary hydroxyproline output. Burn patients, compared with normal individuals, demonstrated a doubling in proline and leucine flux (P less than 0.01 for both findings), a threefold enhancement of proline oxidation (P less than 0.05), a trend toward decreased proline synthesis, and a 37% reduction in plasma proline concentrations (P less than 0.05). Further, the injured group, unlike the control group, was in a distinct negative body proline balance, as proline oxidation greatly exceeded endogenous proline biosynthesis (P less than 0.01). These studies indicate that significant proline deficits may evolve during the postabsorptive period in severely burned patients and that an exogenous supply of proline might benefit the nitrogen economy of the traumatized patient.