A rapid high performance liquid chromatographic method for the analysis of choline in human plasma and peritoneal dialysis effluent: application in the assessment of choline loss in continuous ambulatory peritoneal dialysis.

Mesothelial cells lining the peritoneal cavity utilize choline in the synthesis of a phosphatidylcholine-rich material thought to play a role in peritoneal homeostasis. This function is particularly important for patients undergoing continuous ambulatory peritoneal dialysis (CAPD). To assess choline loss in these patients, we measured choline in plasma and peritoneal dialysis effluent (PDE) by a rapid high performance liquid chromatography (HPLC) procedure that combined electrochemical detection with an immobilized enzyme reactor. Chromatography was performed directly on plasma and PDE ultrafiltrates. In 30 patients, the amount of choline lost to the dialysate was 129 +/- 49 mumol per day and 32 +/- 8 mumol per dwell (mean +/- SD). The average plasma choline concentration was 22.5 mumol/L, a value somewhat higher than the mean value reported for normal adults (9 mumol/L). The average PDE choline concentration was 14 mumol/L. There was a positive correlation between daily choline loss of dialysate and plasma choline concentrations (r = 0.826).

Choline incorporation into phospholipids in mesothelial cells in vitro.

OBJECTIVE: To determine the effect of extracellular choline concentration on phospholipid production and handling by peritoneal mesothelial cells in vitro. DESIGN AND MEASUREMENTS: Radiolabeled choline was used to monitor the formation of phosphatidylcholine (PC), sphingomyelin (SPH), and lysophosphatidylcholine (LPC) by rat and rabbit mesothelial cells as a function of concentration and time of exposure to choline. The subcellular location of the newly formed phospholipids was examined by ultracentrifugation in Percoll-sucrose gradients using analytical cell fractionation techniques. The fatty acid composition of the PC formed was determined by thin-layer chromatography (TLC) and gas chromatography. RESULTS: Choline incorporation into PC, SPH, and LPC increased with extracellular choline levels up to 640 mumol/L, which is 100 times greater than physiological levels of choline in plasma and 20 times higher than choline levels measured in peritoneal dialysis effluent. The newly formed, radiolabeled phospholipids were primarily found in a single subcellular compartment that exhibited a buoyant density of 1.05 g/mL in Percoll-sucrose gradients. Analysis of the fatty acyl groups of PC obtained from the mesothelial cells showed enrichment in palmitic [16:0], oleic [18:1], and linoleic [18:2] acids. CONCLUSION: The rate of phospholipid formation by mesothelial cells in vitro can be manipulated, in part, by choline concentration.

Choline levels in human peritoneal dialysate.

The average free choline level was determined to be 14 mumol/L in peritoneal dialysates and 22 mumol/L in the plasma of 30 patients on continuous ambulatory peritoneal dialysis (CAPD). Daily choline loss via dialysate averaged 129 mumol with 32 mumol choline lost per dwell. Daily choline loss via the dialysate was positively correlated with plasma choline concentrations. Choline levels in dialysate during CAPD exceed plasma levels of choline 9 mumol/L in healthy individuals.

Choline levels in human peritoneal dialysate.

The average free choline level was determined to be 14 M in peritoneal dialysates and 22 M in plasma of thirty patients on continuous ambulatory peritoneal dialysis (CAPD). Daily choline loss via dialysate averaged 129 moles with 32 moles choline lost per dwell. Daily choline loss via the dialysate was positively correlated with plasma choline concentrations. Choline levels in dialysate during CAPD exceed plasma levels of choline (9 M) in healthy individuals.

Functional characteristics of lymphocytes isolated from the rat large intestine. Response to T-cell mitogens and natural killer cell activity.

Using successive ethylenediaminetetraacetic acid and collagenase treatments, two fractions of mucosal lymphocytes have been isolated from the rat large intestine that differ in morphologic and functional characteristics. Intraepithelial lymphocytes consisted largely of granular lymphocytes (91 +/- 6%) that did not respond to stimulation with phytohemagglutinin or concanavalin A, but had natural killer cytotoxic activity against the YAC-1 cell line. The natural killer cytotoxicity of the intraepithelial lymphocytes was specifically reduced by the addition of increasing numbers of unlabeled homologous tumor cells but not by unlabeled thymocytes. The sensitivity of different target cell lines to lysis by intraepithelial lymphocytes was the same as splenocytes from the same rat strain. Lymphocytes from the lamina propria contained 21 +/- 4% granular cells with the remainder being typical small lymphocytes. The lamina propria fraction responded well to stimulation with concanavalin A, phytohemagglutinin, and pokeweek mitogen, and also had natural killer activity against YAC-1 cells.