Factors influencing response of mammalian species to the methaemoglobin reduction test.

Abstract

SummaryFactors influencing variations observed with mammalian species in response to the methaemoglobin reduction test have been investigated by extending the test to include measurements of the stability of “intact” haemoglobin (methaemoglobin plus oxyhaemoglobin) and of the stability of reduced glutathione, by modifying the conditions of the test and by comparing the results obtained with the rates of methaemoglobin reduction in erythrocytes from the various species. The rate of methaemoglobin reduction in the presence of methylene blue seemed in general the most important inverse determinant of the amount of residual methaemoglobin, not only by the obvious effect but also by influencing directly the degree of “intact” haemoglobin destruction. In addition, evidence was obtained of intrinsic susceptibility to oxidative destruction in haemoglobin of the ox and guinea pig, and of a very rapid rate of methaemoglobin reduction in the absence of methylene blue in the rabbit. Discrepant degrees of accumulation of methaemoglobin were associated with instability of reduced glutathione in the sheep, dog and cat. The results appeared to support the concept that the extended methaemoglobin reduction test evaluates the overall erythrocytic response to redox stress, rather than merely the functional capacity of the pentose phosphate pathway.