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PARTITIONING OF BENZENE IN SICKLE CELL BLOOD AND NORMAL BLOOD AND IN THE BLOOD OF THE GUINEA PIG, MOUSE, AND RAT
Wiester, M. J., D. W. Winsett, J H. Richards, D L. Doerfler, AND D L. Costa. PARTITIONING OF BENZENE IN SICKLE CELL BLOOD AND NORMAL BLOOD AND IN THE BLOOD OF THE GUINEA PIG, MOUSE, AND RAT. ENVIRONMENTAL HEALTH PERSPECTIVES 110(3):255-261, (2002).
Benzene was used as a prototypic volatile organic chemical to ascertain whether the insoluble form of hemoglobin (HbS) from subjects with homozygous sickle cell disease (SCD) has a greater VOC carrying capacity than hemoglobin (Hb) from normal subjects (HbA) which is water soluble. This hypothesis was derived from observations that benzene solubility is ~100% higher in the blood of rats than in HbA blood; thought to be attributed to the quasi-crystalline form of rat Hb. Blood (HbA, HbS, Hartley guinea pig, CD1 mouse, and F-344, Wistar, and Sprague-Dawley rats) was exposed to benzene vapor (80 or 400 ppm) in atmospheres of air or in venous- type (low O2) or arterial-type (high O2) gas mixtures for 3 hr at 37 oC in air-tight vials. The blood:gas partition coefficient (PC), Hb, blood gas, pH, and % sickle cells (SC) were measured following equilibration. Benzene concentration did not affect the measurements. The venous-type gas caused the expected changes in blood gas and pH along with an increase in the SC count in HbS blood (~85% compared to ~15% in air or arterial-type atmospheres). There were no SC's in HbA blood. The benzene PC was increased in venous-type HbS blood and dependent on the Hb concentration. In contrast, PC's for arterial- and venous-type HbA blood and the arterial-type of HbS blood were not different and were independent of Hb content. PC's for HbS and HbA blood plasma were not different regardless of atmosphere. The PC for guinea pig blood was similar to human HbA blood. However, PC's for mouse and rat blood were ~100% higher than HbA blood at the same Hb concentration and very dependent on Hb concentration. Data indicate that the benzene carrying capacity for HbS increases when it switches over to the insoluble form in the venous blood which may affect the delivery of benzene to target tissues in subjects suffering from SCD.