RENAL SODIUM HANDLING WITH CYCLOSPORINE-A AND FK506 AFTER ORTHOTOPIC LIVER-TRANSPLANTATION

Hypertension is common after orthotopic liver transplantation and may be due, in part, to cyclosporin A-induced renal dysfunction and/or enh anced proximal tubular sodium reabsorption. To determine whether enhan ced proximal tubular sodium reabsorption is central to the development of posttransplant hypertension, measurements of renal hemodynamics an d fractional clearances of lithium and sodium were compared 1 month af ter orthotopic liver transplantation in previously normotensive patien ts receiving either cyclosporin A (N = 24) or FK506 (N = 18), an immun osuppressive agent that is structurally unlike cyclosporin A and that has a lower reported incidence of hypertension. Median prednisone dose s were 20 and 13 mg/day in the cyclosporin A and FK506 groups, respect ively (P < 0.05). At 1 month, mean arterial blood pressure was higher in the cyclosporin A versus the FK506 group: 108 +/- 2 versus 95 +/- 3 mm Hg (P < 0.05). GFR, RBF, and renal vascular resistance were not di fferent between the two groups: 59 +/- 4 and 53 +/- 5 ml/min per 1.73 m(2), 439 +/- 28 and 440 +/- 41 ml/min per 1.73 m(2), and 22,429 +/- 1 ,822 and 22,977 +/- 3,506 dyne s/cm(5) per 1.73 m(2), respectively. Fr actional lithium excretion was similar in the cyclosporin A and FK506 groups: 19.9 +/- 2.2 and 19.4 +/- 2.0% (P = not significant) although both values were lower than those of normal controls (25.5 +/- 1.1%) ( P < 0.05). Fractional sodium excretion was 2.7 +/- 0.3 and 2.3 +/- 0.4 % in the cyclosporin A and FK506 groups, respectively (P = not signifi cant). These results indicate that proximal sodium reabsorption is enh anced to a similar degree during treatment with either cyclosporin A o r FK506 after orthotopic liver transplantation and cannot per se expla in the different incidence of hypertension between the two groups.