FREE AND ESTERIFIED CARNITINE IN CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS PATIENTS

Free, acetyl-, medium- and long-chain acylcarnitine and total plasma c arnitine concentrations were measured in eight continuous ambulatory p eritoneal dialysis (CAPD) patients and eight age- and sex-matched heal thy controls. Daily loss of carnitine was also quantified in both grou ps, by analysis of urine and dialysis fluid. Plasma total carnitine co ncentration in CAPD patients was not significantly different from cont rols (42.8 +/- 1.6 and 43.1 +/- 2.3 mu mol/liter, respectively). Howev er, the plasma free carnitine concentration of CAPD patients was signi ficantly lower than that of controls (28.5 +/- 1.4 and 36.2 +/- 2.5 mu mol/liter, respectively; P < 0.05). No difference in the daily loss o f total carnitine was found between CAPD patients and controls (269.7 +/- 30.0 and 240.5 +/- 33.0 mu mol, respectively), but the daily loss of free carnitine was significantly greater in CAPD patients (175.8 +/ - 17.3 and 105.8 +/- 16.4 mu mol, respectively; P < 0.05). The ratio o f total acylcarnitine (acetyl-, medium- and long-chain acylcarnitine) to free carnitine was significantly greater in plasma of CAPD patients than in controls (P < 0.01) and was lower in daily fluid losses (P < 0.001). These ratio differences suggests that an alteration in acyl gr oup metabolism is occurring in CAPD patients. This may be attributable to an accumulation of medium- and long-chain acylcarnitine in liver o f CAPD patients which would be exchanged for plasma free carnitine and /or to a differential loss of free and acylcarnitine across the perito neal cavity.