Effect of methylene chloride on the oxyhemoglobin dissociation curve of rat and human blood

Abstract Methylene chloride is biotransformed in vivo to carbon monoxide (CO), and increased carboxyhemoglobin (COHb) concentrations occur in animals and man following exposure. Binding of CO to hemoglobin causes a shift to the left in the position of the oxyhemoglobin dissociation curve (ODC), theoretically resulting in a diminished ability to release oxygen in tissue. This study was designed to determine the effect of methylene chloride alone and in combination with CO on altering the ODC. Methylene chloride and CO, alone and in combination, were incubated with rat and human blood in vitro and the position of the ODC was measured by the P50 value. The results indicate clearly that methylene chloride alone had no effect on changing the P50 value of the ODC. It was concluded that any shift to the left of the ODC following exposure to methylene chloride is due solely to CO formed from the biotransformation of methylene chloride. Thus, speculation that methylene chloride increases the affinity of Hb for CO is not supported.