GLOMERULAR BARRIER FUNCTION FOLLOWING CONVERSION FROM CYCLOSPORINE TOAZATHIOPRINE IN RENAL-TRANSPLANT RECIPIENTS

The renal side effects are the major limitation of the use of cyclospo rine in clinical transplantation. We studied the reversibility of chan ges in renal hemodynamics and glomerular barrier function in 17 patien ts with moderately impaired renal function at least 1 year after kidne y transplantation. All patients were studied both during cyclosporine treatment and 3 months after conversion to azathioprine. During azathi oprine treatment both glomerular filtration rate and effective renal p lasma flow increased significantly (from 44.3 +/- 4.2 mL/min to 63.5 /- 5.4 mL/min and from 192 +/- 12.8 mL/min to 260 +/- 14.6 mL/min, res pectively). Despite the marked changes in renal hemodynamics, no signi ficant changes were observed in the fractional clearances of uncharged dextrans. When calculating the characteristics of the filtration barr ier, we observed a trend toward an increase in the ultrafiltration coe fficient (K-f). This trend was abolished when an increase in net filtr ation pressure (Delta P) was assumed to result from reduced prerenal v asoconstriction. We conclude that despite marked improvement of renal perfusion and glomerular filtration, conversion from cyclosporine to a zathioprine did not significantly alter the permeability characteristi cs of the glomerular filtration barrier in renal transplant recipients with moderately reduced renal function. Improvement in renal function following conversion could result from an increase in either K-f or D elta P. Since renal plasma flow was increased significantly, the obser ved improvement in glomerular filtration rate is likely to be, at leas t in part, due to an increase in glomerular capillary plasma flow. (C) 1994 by the National Kidney Foundation, Inc.