Our recent work on Black Rhinoceros red blood cell (RBC) metabolism
has revealed a unique metabolic process in which very high intracellular
levels of the free amino acid tyrosine assist in elimination of
ambient oxidants such as hydrogen peroxide.
The subsequent observation of lower levels of RBC tyrosine in
captive than in in situ animals, and the additional observation
of an inverse relationship between ferritin levels (reflecting
iron overload) and RBC tyrosine levels, pointed very strongly
to a pathology caused by oxygen free radicals, consequent to iron
overload, in which defense processes including the scavenging
of oxidants by RBC tyrosine proved insufficient.
The research design of this project therefore aims to comprehensively
define the processes by which tyrosine in the Black Rhinoceros
RBC eliminates ambient oxidants. It will also compare this process
in other rhino species known to possess high RBC tyrosine, confirm
(or otherwise) its unique presence in the Rhinocerotidae, confirm
the specificity for these reactions to the red blood cell, and
investigate any interaction with iron or copper ions.
Measurements of RBC ATP will proceed in parallel. In collaboration
with laboratories in the USA, serum iron, TIBC, and ferritin,
as well as RBC tyrosine, dityrosine and ATP will be compared both
in wild rhinos in Southern Africa and in captive animals in the
USA, to confirm the suspected inverse relationship between iron
overload and RBC tyrosine and to confirm their association with
the various disease states.
This information should lead to a final phase in which the effect
of dietary factors such as iron chelators and antioxidants can
be studied, monitoring ferritin and RBC tyrosine levels in particular,
to determine whether introduction of such dietary components to
the feed of captive Black Rhinoceroses can prevent or treat the
common disease states.