Two soluble tumor necrosis factor receptors (sTNFRs) were detected in the plasma of patients with different degrees of chronic renal failure (CRF) and of long-term hemodialysis (HD) patients. In uremic undialyzed patients, plasma levels of both sTNFRs increased progressively with declining renal function. A linear correlation was found between sTNFR plasma levels and plasma creatinine concentration. sTNFR levels in end-stage uremic patients shortly before commencement of first HD treatment were approximately tenfold higher than in normal subjects. Long-term HD patients showed a further increase in plasma sTNFRs. The origin of sTNFRs, as well as their physiological role remains to be elucidated.
We quantified the plasma levels and peritoneal loss of lipids and lipoproteins, and studied the composition of plasma and effluent lipoproteins in 16 patients on CAPD (5 females and 11 males, 18 to 76 years old). Five patients were studied prospectively (at 0, 1, 3 and 6 months) and 11 patients at 6 to 58 months on CAPD (N = 30). Elevated levels of plasma VLDL and reduced levels of plasma HDL were maintained in these patients throughout 58 months of CAPD, whereas the initially increased LDL levels showed a tendency towards normalization. All plasma lipoproteins (VLDL, IDL, LDL and HDL) were present in the peritoneal effluent. The lipoproteins isolated from plasma and peritoneal fluid shared a similar lipid and apolipoprotein composition. The peritoneal transport characteristics of plasma lipoproteins were similar to other plasma macromolecules. Their clearance correlated with their molecular mass, plasma concentration and dwell time, but was not affected by duration of CAPD treatment. The plasma lipid and lipoprotein levels were unaffected by the rate of glucose absorption. The peritoneal protein clearance correlated positively with plasma levels of triglyceride and LDL, and negatively with plasma HDL. An inverse correlation was observed also between plasma levels of HDL and its peritoneal clearance (r = -0.393, P less than 0.025, N = 30). The continuous peritoneal loss of HDL and the hypertriglyceridemia were found to contribute most to the persistent low plasma levels of HDL in CAPD patients, and thus may lead to the accelerated atherosclerosis observed in these patients.
We studied the peritoneal protein loss in 13 patients during CAPD using 2 liters of 1.5% dextrose dialysis solutions. We compared the kinetic characteristics of the peritoneal mass transfer and clearance of proteins over a wide range of molecular size, to those of small molecular weight solutes. The peritoneal clearance of all studied proteins and solutes correlated strongly and negatively with their molecular mass. No changes were observed in these clearances during 58 months of dialysis. Unlike the peritoneal mass transfer and clearance of small molecular weight solutes (less than 200) which revealed a remarkable progressive drop after the first hour of an eight-hour dialysis cycle, the mass transfer and clearance of proteins of large molecular weight (greater than 68,000) was continuous throughout the eight hours. The clearance of proteins of small molecular weight (less than 15,000) showed similar kinetics to small solutes (less than 200). These results indicate that long dwell times (6 or 8 hr) of peritoneal dialysis are detrimental for the loss of large molecular weight proteins (such as albumin and immunoglobulins) in view of the negligible dialysance of both small solutes (creatinine and potassium) and "intermediate molecules" (represented by the small molecular weight proteins) during the latter hours of long dwell cycles. Thus we suggest that substituting CAPD (3 x 8 hr or 4 x 6 hr) with CCPD (6 x 1 hr) may limit protein loss in these patients.
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