IMPAIRED RENAL TUBULAR POTASSIUM SECRETION IN SICKLE-CELL DISEASE

Renal tubular function was examined in 6 patients with sickle cell Hb. All had normal inulin and paraaminohippurate clearances and impaired urinary concentrating and acidifying abilities. After i.v. KCl administration, maximum excretion of K (UV) was significantly lower in sickle cell patients than in control subjects, and the percentage of K load excreted in 5 h was markedly reduced. Urinary K excretion after sodium sulfate infusion was also markedly reduced in sickle cell patients compared to control subjects. After 40 mg of oral furosemide, UV was also diminished in sickle cell patients. Plasma aldosterone response to ACTH and i.v. was similar to that of control subjects. Plasma renin activity increased normally after volume contraction. Sickle cell patients have a defect in their ability to excrete an acute K load that cannot be attributed to abnormal renin or aldosterone secretion. Overall K homeostasis is maintained by extrarenal mechanisms during acute K loading.