Differential effects of volatile anesthetics on hepatic heme oxygenase-1 expression in the rat.

THE microsomal enzyme heme oxygenase (HO; EC 1.14.99.3) catalyzes the oxidation of heme to biliverdinIXa, iron, and carbon monoxide. So far, three isoforms of this enzyme have been cloned. While HO-2 and HO-3 are constitutively expressed, HO-1 is highly inducible in response to a variety of stimuli and has been identified as the major 32-kd heat shock (stress) protein (HSP) 32. Heme oxygenase–1 is essential for the function of the normal liver and plays a major protective role in the stress-exposed liver. It exerts antioxidant properties by cleavage of the prooxidant heme and by the production of biliverdin, which is subsequently reduced to the antioxidant bilirubin. Furthermore, its product carbon monoxide serves to maintain liver perfusion and has potent antiinflammatory effects. Many studies have shown differential effects of volatile anesthetics on the perfusion, function, and integrity of the liver. Moreover, preliminary evidence suggests that volatile anesthetics may interfere with stress gene expression and function. We therefore aimed to determine whether volatile anesthetics affect hepatic HO-1 gene expression.