INTERACTIONS OF ULTRAPURE BOVINE HEMOGLOBIN WITH RENAL EPITHELIAL-CELLS IN-VIVO AND IN-VITRO

Using an ultrapurified hemoglobin (Hb) solution, we investigated the p hysiological effects and cellular processing of Hb in rat kidneys and in cultured opossum kidney (OK) cells. Rats infused with <5.0 g/kg Hb showed no change in baseline serum creatinine (Sc,) values (0.58 +/- 0 .05 mg/dl) over 48 h, whereas transient acute renal failure followed i nfusion of 7.5 g/kg Hb (S-Cr 3.4 +/- 1.02 mg/dl, P = 0.02). Histology of Hb-infused kidneys demonstrated tubular epithelial cell injury. Ren al injury was not caused by volume or oncotic load, cardiovascular eff ect, or ATP depletion. After Hb infusion, heme oxygenase, the rate-lim iting enzyme in Hb catabolism, was induced in an organ-specific fashio n. Inhibiting heme oxygenase activity with cimetidine did not alter Hb renal injury. Using OK cells, we determined that renal epithelia proc ess Hb by fluid-phase endocytosis. Proton permeability of fluorescein Hb endosomes was unaltered compared with fluorescein dextran controls, demonstrating that Hb does not alter endosomal membrane integrity. Th ese data suggest that Hb renal injury in rats occurs following large d oses of ultrapure Hb, does not alter early steps in Hb endosomal proce ssing by renal epithelia, and involves a mechanism that is not heme ox ygenase dependent.