Chronic Copper Poisoning in Sheep. I. The Relationship of Methaemoglobinemia to Heinz Body Formation and Haemolysis during the Terminal Crisis

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Abstract
The values of hematocrit, total Hb in plasma, methemoglobin [metHb] percentages in erythrocytes and plasma, osmotic fragility of the erythrocytes, and the occurrence of Heinz bodies were investigated during the terminal crisis in 4 cases of experimental chronic Cu poisoning in Norwegian sheep. At the beginning of the crisis, which lasted more than 1 day, 10-20% metHb was detected in the erythrocytes before any hemolysis occurred. Later, severe hemolysis developed and maximum levels of Hb in the plasma were close to 2.5 g/100 ml. During the hemolytic stage both metHb and Hb 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 hemolysis. MetHb formation is mainly an intra-corpuscular process. Most of the metHb detected in plasma in chronic Cu poisoning in sheep comes from the erythrocytes.