Renal toxicodynamic effects of extracellular hemoglobin after acute exposure

Abstract

Plasma hemoglobin (Hb) is elevated in some hematologic disease states, during exposures to certain toxicants, and with the use of some medical devices. Exposure to free Hb can precipitate oxidative reactions within tissues and alter the normal physiological function of critical organ systems. As kidney structures can be highly sensitive to Hb exposures, we evaluated the acute dose dependent renal toxicologic response to purified Hb isolated from RBCs. Male Hartley guinea pigs (n ¼ 5 per group) were dosed with 0.9% saline (2 ml), 15, 75, 150, or 300 mg of purified Hb, infused over a 2-h period. The primary endpoints of this study were to define toxicokinetic parameters after increasing doses of purified Hb, identify clinically recognized and experimental markers of acute kidney injury (AKI), and determine relevant toxicological parameters and potential causes of renal toxicity in this model. Experimental findings demonstrated a dose dependent increase in Cmax after a 2-h infusion, which correlated with an elevation in serum creatinine, renal Kim-1 mRNA expression and increased urinary Kim-1. Renal NGAL mRNA expression and urinary NGAL excretion were also increased in several groups, but these parameters did not correlate with exposure. Iron increased in the renal cortex as Hb exposure increased and its deposition colocalized with 4-hydroxy-nonenal and 8-Oxo-2-deoxyguanosine immune reactivity, suggesting oxidative stressors may contribute to AKI in animals exposed to Hb. The results presented here suggest that Cmax may effectively predict the risk of AKI in normal healthy animals exposed to Hb.