Chronic copper poisoning in sheep. I. The relationship of methaemoglobinemia to Heinz body formation and haemolysis during the terminal crisis.

The values of haematocrit, total haemoglobin in plasma, methaemoglobin percentages in erythrocytes and plasma, the osmotic fragility of the erythrocytes, and the occurrence of Heinz bodies were investigated during the terminal crisis in 4 cases of experimental chronic copper poisoning in sheep. At the beginning of the crisis, which lasted for well over one day, 10-20 per cent methaemoglobin was detected in the erythrocytes, before any haemolysis occurred. Later on severe haemolysis developed, and maximum levels of haemoglobin in the plasma were close to 2.5 g/100 ml. During the haemolytic stage both methaemoglobin and haemoglobin were detected in the plasma at approximately the same proportions as in the erythrocytes. No changes were observed in the osmotic fragility of the red cells until the onset of the haemolysis. It is concluded that the methaemoglobin formation is mainly an intra-corpuscular process and that most of the methaemoglobin detected in plasma in chronic copper poisoning in sheep, comes from the erythrocytes.