The tripeptide, reduced glutathione (GSH), is present in high
concentration in mammalian erythrocytes, where its major role is the
protection of the cell against oxidative damage. Sheep exhibit two
distinct types of erythrocyte GSH deficiency. In Finnish Landrace
sheep (Finns) low GSH is inherited as an autosomal recessive trait,
and is associated with a markedly diminished erythrocyte life-span,
and the presence of unusually high concentrations of some erythrocyte
amino acids, notably ornithine and lysine. In contrast, in Tasmanian
Merino sheep (Merinos) the low GSH characteristic is inherited in an
autosomal dominant manner and both the erythrocyte life-span and
amino acid concentrations are normal. This Thesis describes an
investigation of the biochemical mechanisms responsible for the Finn
and Merino erythrocyte GSH deficiencies.
The Finn and Merino sheep investigated were maintained by the ARC
Animal Breeding Research Organisation, Edinburgh. Both breeds
contained substantial numbers of GSH-deficient animals. In agreement
with other studies, GSH-deficient Finn erythrocytes were found to
contain very high concentrations of ornithine and lysine, a phenomenon
not encountered in Merinos.
Sheep were allotted their GSH type on the basis of their
erythrocyte total non-protein reduced thiol concentration as determined
by the non-specific thiol reagent 5, 5'-dithiobis-(-2-nitrobenzoate)
(DTNB). The validity of equating total DTNB reactive thiol with GSH
was established by estimating GSH using novel automated versions of
methods employing DTNB and alloxan as chromogens. GSH-deficient
erythrocytes of both breeds were also found to have a diminished
GS3G concentration so that they had a diminished total glutathione
content (GSH + 2GSSG). The alloxan GSH and GSSG estimates were
used to calculate the redox potential of the GSH:G3SG couple in the
various cell types. In both breeds the difference in redox potential
between normal and GSH-deficient cells was small. It is suggested that
the diminished life-span of GSH-deficient Finn cells may not be a
direct consequence of their GSH status
