The effect of dialysate acidity on peritoneal solute transport in the rat.

OBJECTIVE

To investigate the possible effect of unphysiologically low pH in dialysis fluid on peritoneal transport.

DESIGN

A 4-hour single-cycle experimental session of peritoneal dialysis was performed in six Sprague-Dawley rats using Dianeal 3.86% solution modified by adding 5 mmol/L of sodium hydroxide, neutral pH solution (NpHS) (pH 7.4). The intraperitoneal volume (VD) and peritoneal bulk fluid reabsorption (Qa) were calculated using a marker, 131I-labeled human serum albumin (RISA). The diffusive mass transport coefficient (KBD) as well as sieving coefficient (S) for glucose, urea, sodium, and potassium were calculated using the Babb-Randerson-Farrell model. The same study was performed in seven rats using Dianeal 3.86% solution, acidic pH solution (ApHS) (pH 5.7) to provide control values.

RESULTS

The dialysate pH was stable with NpHS; 45 min after the infusion of ApHS it increased rapidly and reached the physiological value 7.4. Dialysate volume and KBD values for sodium and potassium with NpHS were significantly higher than with ApHS, while the KBD values for glucose and urea did not differ between the two solutions. S values for sodium and urea did not differ between the two solutions, while the values for glucose and potassium with NpHS were significantly higher and lower, respectively, than the values with ApHS (0.92 +/- 1.04 vs 0.04 +/- 0.63 and 0.56 +/- 060 vs 1.15 +/- 0.39, p < 0.05). The absorption of glucose from the dialysis solution expressed as a percentage of the initial amount of dialysate glucose was significantly lower with NpHS than with ApHS at 30 min (17.3 +/- 1.7% vs 29.7 +/- 2.0%, p < 0.05).

CONCLUSION

We conclude that the peritoneal transport of fluid and small solutes might to some extent be influenced by the acidity of the dialysis solution. The vasodilatory effect of acidic dialysis solution might be the most important mechanism for these differences. However, a larger KBD value and a lower S value for potassium and higher S values for glucose during dialysis with the neutral dialysis solution may indicate that transport mechanisms other than simple passive transport are involved in peritoneal transport for glucose and electrolytes.