OBJECTIVE: Glucose-based dialysate induces non enzymatic glycation within the peritoneal cavity. To evaluate the relationship between the formation of advanced glycation end-products (AGEs) and peritoneal transfer for small solutes and macromolecules, we developed a model of simulated peritoneal dialysis (PD) in normal rats. METHODS: Male albino rats of the Charles River strain were divided into two sets of 3 groups (15-25 rats in each group). In the experimental (E) group, the rats were intraperitoneally (i.p.) injected daily with a commercially available 4.25% dextrose solution. In the control puncture (CP) group, the peritoneum was punctured daily, but no PD solution infused. In an age-matched control (CC) group, no intervention was given. Two study protocols were used. Protocol A (duration 20 weeks) consisted of a daily i.p. injection of 10 mL PD solution per 100 g body weight. In protocol B, a double volume of PD solution was introduced (20 mL per 100 g body weight). At 9, 16, and 20 weeks in protocol A, and at 9 weeks in protocol B, urea, creatinine, microalbumin [(MAL) measured using specific anti-rat albumin monoclonal antibody], and AGEs (measured by fluorescent assay with excitation at 370 nm and emission at 440 nm) were measured in peritoneal effluent and serum. RESULTS: At no time during the study were AGEs detected in serum from any group in either protocol. In both protocols, no differences were found between the control groups (CP, CC) with respect to all parameters. In protocol A, the dialysate-to-plasma ratio (D/P) of urea was significantly higher in the experimental group as compared with the control groups at 9, 16, and 20 weeks [9 weeks: 0.59 +/- 0.03 (E) vs 0.39 +/- 0.02 (CP) vs 0.46 +/- 0.02 (CC), p < 0.0004 and p < 0.002, respectively; 16 weeks: 0.71 +/- 0.08 (E) vs 0.42 +/- 0.01 (CP) vs 0.46 +/- 0.01 (CC), p < 0.0001 and p < 0.02, respectively; 20 weeks: 0.57 +/- 0.03 (E) vs 0.39 +/- 0.01 (CP) vs 0.41 +/- 0.02 (CC), p < 0.002 and p < 0.004, respectively]. At 16 and 20 weeks, dialysate MAL levels were significantly increased in group E [16 weeks: 354.00 +/- 80.35 microg/mL (E) vs 134.75 +/- 14.36 microg/mL (CP) vs 110.69 +/- 7.83 microg/mL (CC), p < 0.04 and p < 0.03, respectively; 20 weeks: 283.17 +/- 14.71 microg/mL (E) vs 105.14 +/- 12.11 microg/mL (CP) vs 135.50 +/- 19.03 microg/mL (CC), p < 0.00001 and p < 0.0001, respectively]. In protocol B, at completion of the study (week 9), D/P urea, effluent MAL, and AGEs were significantly higher in the experimental group as compared with the control groups [D/P: 0.67 +/- 0.04 (E) vs 0.46 +/- 0.07 (CP) vs 0.41 +/- 0.02 (CC), p < 0.0002 and p < 00001, respectively; MAL: 336.8 +/- 63.30 microg/mL (E) vs 125.71 +/- 16.77 microg/mL (CP) vs 119.00 +/- 39.75 microg/mL (CC), p < 0.008 and p < 0.007, respectively; AGEs: 265.77 +/- 33.49 U/mg creatinine (E) vs 163.10 +/- 21.99 U/mg creatinine (CP) vs 83.17 +/- 22.66 U/mg creatinine (CC), p < 0.02 and p < 0.001, respectively]. Peritoneal effluent AGEs were found to be significantly correlated with D/P urea and dialysate MAL (r = 0.42, p < 0.04, and r = 0.7, p = 0.00001, respectively). CONCLUSIONS: In situ generation of AGEs constitutes the chief origin of peritoneal AGEs. Advanced glycation end-products affect peritoneal permselectivity for both small and large solutes. The rat model of simulated peritoneal dialysis developed in this experiment provides a reliable method for studying peritoneal AGE formation and effect on peritoneal transfer of small solutes and macromolecules.
OBJECTIVE:Glucose-based dialysate induces non enzymatic glycation within the peritoneal cavity. To evaluate the relationship between the formation of advanced glycation end-products (AGEs) and peritoneal transfer for small solutes and macromolecules, we developed a model of simulated peritoneal dialysis (PD) in normal rats. METHODS: Male albino rats of the Charles River strain were divided into two sets of 3 groups (15-25 rats in each group). In the experimental (E) group, the rats were intraperitoneally (i.p.) injected daily with a commercially available 4.25% dextrose solution. In the control puncture (CP) group, the peritoneum was punctured daily, but no PD solution infused. In an age-matched control (CC) group, no intervention was given. Two study protocols were used. Protocol A (duration 20 weeks) consisted of a daily i.p. injection of 10 mL PD solution per 100 g body weight. In protocol B, a double volume of PD solution was introduced (20 mL per 100 g body weight). At 9, 16, and 20 weeks in protocol A, and at 9 weeks in protocol B, urea, creatinine, microalbumin [(MAL) measured using specific anti-rat albumin monoclonal antibody], and AGEs (measured by fluorescent assay with excitation at 370 nm and emission at 440 nm) were measured in peritoneal effluent and serum. RESULTS: At no time during the study were AGEs detected in serum from any group in either protocol. In both protocols, no differences were found between the control groups (CP, CC) with respect to all parameters. In protocol A, the dialysate-to-plasma ratio (D/P) of urea was significantly higher in the experimental group as compared with the control groups at 9, 16, and 20 weeks [9 weeks: 0.59 +/- 0.03 (E) vs 0.39 +/- 0.02 (CP) vs 0.46 +/- 0.02 (CC), p < 0.0004 and p < 0.002, respectively; 16 weeks: 0.71 +/- 0.08 (E) vs 0.42 +/- 0.01 (CP) vs 0.46 +/- 0.01 (CC), p < 0.0001 and p < 0.02, respectively; 20 weeks: 0.57 +/- 0.03 (E) vs 0.39 +/- 0.01 (CP) vs 0.41 +/- 0.02 (CC), p < 0.002 and p < 0.004, respectively]. At 16 and 20 weeks, dialysate MAL levels were significantly increased in group E [16 weeks: 354.00 +/- 80.35 microg/mL (E) vs 134.75 +/- 14.36 microg/mL (CP) vs 110.69 +/- 7.83 microg/mL (CC), p < 0.04 and p < 0.03, respectively; 20 weeks: 283.17 +/- 14.71 microg/mL (E) vs 105.14 +/- 12.11 microg/mL (CP) vs 135.50 +/- 19.03 microg/mL (CC), p < 0.00001 and p < 0.0001, respectively]. In protocol B, at completion of the study (week 9), D/P urea, effluent MAL, and AGEs were significantly higher in the experimental group as compared with the control groups [D/P: 0.67 +/- 0.04 (E) vs 0.46 +/- 0.07 (CP) vs 0.41 +/- 0.02 (CC), p < 0.0002 and p < 00001, respectively; MAL: 336.8 +/- 63.30 microg/mL (E) vs 125.71 +/- 16.77 microg/mL (CP) vs 119.00 +/- 39.75 microg/mL (CC), p < 0.008 and p < 0.007, respectively; AGEs: 265.77 +/- 33.49 U/mg creatinine (E) vs 163.10 +/- 21.99 U/mg creatinine (CP) vs 83.17 +/- 22.66 U/mg creatinine (CC), p < 0.02 and p < 0.001, respectively]. Peritoneal effluent AGEs were found to be significantly correlated with D/P urea and dialysate MAL (r = 0.42, p < 0.04, and r = 0.7, p = 0.00001, respectively). CONCLUSIONS: In situ generation of AGEs constitutes the chief origin of peritoneal AGEs. Advanced glycation end-products affect peritoneal permselectivity for both small and large solutes. The rat model of simulated peritoneal dialysis developed in this experiment provides a reliable method for studying peritoneal AGE formation and effect on peritoneal transfer of small solutes and macromolecules.