The study investigated the link between the
potentially nephrotoxic levels of aluminium ingested in
the natural diet of eucalypt leaves by koalas in the
Adelaide Hills, South Australia, and the high incidence
of renal failure in koalas within this habitat. Routine
histology of kidney specimens revealed no pathologies
at the light microscopic level and contrasted sharply with
the clinical signs of renal failure. However staining with
solochrome azurine and Perl’s Prussian blue showed
aluminium was present in some proximal convoluted
tubules in all specimens. Aluminium was also found in
bone samples. The presence of aluminium in bone and
kidney tissues was confirmed using electron dispersive
x-ray analysis with transmission and scanning electron
microscopy. Ultrastructural changes, including a
decrease in lysosomal numbers, were seen in proximal
convoluted tubules and these changes were shown to
coincide with the presence of aluminium. No aluminium
was found in koalas that died from causes other than
renal failure. It was concluded that renal failure in the
koalas of the Adelaide Hills is characterised by the
presence of aluminium in the kidneys and bone and it is
probably related to the high levels of aluminium in their
restricted diet of eucalypt leaves. However, it is not
known if the presence of aluminium is the cause or
effect of the renal failure. The study is the first account where aluminium ingested as part of the natural diet of
mammals has been shown to accumulate in the animal
and be implicated with nephrotoxicity