The interactive effect of chlorine, copper and nitrite on methaemoglobin formation in red blood cells of Dorset sheep.

Simultaneous exposure to chemicals which can oxidize the haemoglobin of the red blood cell to methaemoglobin is common. Although the effects of some of these agents have been documented individually, little research considers the interactive effects. In-vitro experiments on the treated blood of female Dorset sheep assessed the interactive capacity of chlorite, copper and nitrite to affect methaemoglobin formation. All combinations of doses which produced 2.5, 5, 10% methaemoglobin were tested in all possible combinations (a total of 80), as were the controls. This included data on each chemical alone, each two-way combination and the three-way combination. The response is largely additive (the sum of the individual effects) except for one of the two-way interactions, chlorite/nitrite (P less than .01), which showed antagonism. Chlorite may oxidize nitrite which could explain the less-than-additive response. Overall, the result of combining these agents on methaemoglobin was additive.