Renal and adrenal mechanisms in cyclosporine-induced hyperkalaemia after renal transplantation.

CsA associated hyperkalaemia was investigated in 24 renal transplant recipients 6 months after transplantation. 51Cr-EDTA-, PAH-, lithium and sodium clearances, 24 h urinary creatinine and potassium excretions, plasma renin activity and aldosterone concentrations were measured. Transtubular potassium concentration gradient (TTKG) was calculated. An ACTH test was performed to document adrenal function. Eleven patients had hyperkalaemia. The TTKGs were low normal or reduced in both normo- and hyperkalaemic patients implying inhibition of K+ secretion. The hyperkalaemic patients received more CsA (mean dose 21.3 vs. 9.7 mg kg-1d-1, P = 0.01), and had lower lithium clearances (mean 9.9 vs. 17.0 mL min-1 1.73 m-2, P < 0.05). Adrenal function had no clear effect. Serum potassium concentration correlated with CsA dose (r = 0.773, P < 0.001) and inversely with lithium clearance (r = -0.568, P < 0.01) suggesting that CsA induced decrease in distal tubular flow rate reduced K+ excretion. Hyperkalaemia was not fully explained by renal mechanisms.