The effects of the acetate content of hemodialysis fluids on the relation between L-carnitine (free carnitine, cr FC) and acetyl-L-carnitine (AC) have not previously been examined in detail. The net fluxes of FC, AC, and acetate between intra- and extracellular pools during hemodialysis were calculated using a kinetic model with dialysates containing three concentrations of FC (0, 40, and 80 mumol/L) and either 40 or 3 mmol acetate/L. Radioenzymatic assays of FC and AC were optimized for use with samples taken during hemodialysis. Acetate stimulated a tissue uptake of FC (P < 0.05) that could exceed the rate of FC delivery and was related to the dialysate FC composition (P < 0.02). There were associated changes in tissue AC output. With dialysate containing 40 mmol acetate/L, AC tissue output was directly related to the dialysate FC composition (P < 0.05). The AC tissue output was less with dialysate containing 3 mmol acetate/L (P < 0.05) but the significant increase with the provision of FC in the dialysate was retained (P < 0.05). Hemodialysis may therefore represent an acute period of relative carnitine deficiency when regeneration of free coenzyme A from acetyl coenzyme A consequent to metabolism of acetate is limited.

The effect of twice daily infusions of 200 mg naftidrofuryl on the six day cumulative losses of urinary nitrogen after moderate surgery was studied in 32 patients maintained on an intravenous infusion of 4% dextrose and saline. A previous report ofthe ability ofnaftidrofuryl to reduce loss of nitrogen was not substantiated, although changes in metabolism in the immediate postoperative period suggested that the drug might exert some advantageous metabolic effect. Further investigations with other nutritional regimens are warranted. IntroductionThe major metabolic effect of trauma or operations is to increase the net degradation of muscle protein to provide alternative energy substrates and to maintain the synthesis of visceral

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