The biochemical properties of red cells from normal sheep and sheep with three types of red cell glutathione (GSH)-deficiency were compared. One deficiency was due to an impaired transport system for amino acids (lesion 1), one was the result of a diminished activity of gamma-glutamyl cysteine synthetase (GC-S) (lesion 2) and the third was a combined deficiency produced by selective breeding to give animals with both lesions 1 and 2. Under normal husbandry conditions no clinical symptoms were apparent in sheep with lesion 2, but red cells from sheep with lesion 1 and lesions 1 + 2 showed an increased osmotic fragility, a greater tendency to form Heinz bodies and a shorter potential life span than normal. These deficiencies were not found in tissues other than blood. Normal and GSH-deficient red cells had the expected low concentrations of 5-oxoproline. The effects of the toxic agents phenylhydrazine, s-methylcysteine sulphoxide and nitrite in vivo were measured in sheep of the different types. GSH-deficient sheep responded earlier and more dramatically than normal sheep, showing greater methaemoglobin formation, and for phenylhydrazine and s-methylcysteine sulphoxide, more severe anaemia. Sheep with the combined lesions were in general the most susceptible, but even they had the ability to recover from moderately severe oxidative challenge.

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Three NADH diaphorase phenotypes were observed in the red cells of sheep. Breeding data indicated that this polymorphism was under the control of two autosomal codominant alleles, designated DiaF and Dias. Phenotype Dia F had significantly lower NADH diaphorase activity than phenotype Dia S . The frzquency of DiaF and DiaS was determined in 9 different breeds.

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