Acute episodic hemolysis in the African black rhinoceros as an analogue of human glucose-6-phosphate dehydrogenase deficiency.

Sudden episodes of massive hemolysis have become the most common cause of death among captive black rhinoceroses, and there is evidence that they occur in the wild as well. We have observed radically unique enzyme and metabolite profiles in normal rhinoceros erythrocytes compared to humans and other mammals, including marked deficiencies of intracellular adenosine triphosphate (ATP), catalase, adenosine deaminase, and other enzymes involved in glycolysis, glutathione cycling, and nucleotide metabolism. Minimal concentrations of ATP appear to impair effective acceleration of hexosemonophosphate shunt activity in response to oxidants by restricting substrate generation at the hexokinase step. Antioxidant defenses are further compromised by catalase deficiency, which may be a general characteristic of rhinoceros erythrocytes, perhaps related to the common occurrence of severe mucocutaneous ulcerative disease. It is proposed that erythrocyte ATP deficiency in rhinoceroses may be an evolutionary adaptation conferring selective advantage against common hemic parasites, comparable to the role of human glucose-6-phosphate dehydrogenase (G-6-PD) deficiency in falciparum malaria.