Background: Many studies have shown that cyclosporine A may have detrimental long-term effect on kidney function. However, few prospective long-term studies have assessed both glomerular and tubular functions of the kidneys in heart transplant recipients
Methods: We examined 10 heart transplant recipients prospectively for 5 years. Hemodynamic data were obtained by standard heart catheterization technique, and glomerular filtration rate and blood flow were calculated as clearance of inulin and paraaminohippuran, respectively. Tubular functions were assessed by renal excretion of enzymes and albumin and by the lithium clearance method. All patients received cyclosporine A, azathioprine, and prednisolone as immunosuppressive regimen. The dose of cyclosporine averaged 3.9 +/- 0.3 during the first year and 3.2 +/- 0.3 mg/kg up to 5 years.
Results: All patients completed the study. Four received rejection therapy. Six were treated for hypertension. Cardiac output remained unchanged and averaged 5.5 +/- 0.9 L/min at baseline. No change ws found in any of the measured or calculated central hemodynamic parameters except a tendency toward an increased systemic peripheral resistance with time. Glomerular filtration remained constant at 66 +/- 22 ml/min, renal plasma flow showed a tendency to decline averaging 361 +/- 133 at baseline and 254 +/- 68 ml/min at 5 years (p = 0.08). Albumin excretion rate increased from 22 +/- 27 to the 102 +/- 100 micrograms/min between 1 and 5 years ( p < 0.05). The excretion of tubular enzymes, N-acetyl-6-glucosaminidase and alkaline phosphatase, and the renal handling of lithium remained unchanged.
Conclusions: Cyclosporine therapy over 5 years did not progressively impair glomerular or tubular functions. However, the occurrence of microalbuminuria may be caused by therapy with cyclosporine itself or associated hypertension.