Lead Toxicity in Mute Swans

Red blood cell protoporphyrin ..
The extraction method followed Peter et al., (1978):
25ul of whole
blood was added to 250ul of normal saline (0.90%) and then 2.5ml of a
mixture of ethyl acetate/acetic acid [ (4/1 vol) Aristar grade] was
added and the solution vortex-mixed for 15s.
A second extraction
transferred protoporphyrin from the ethyl-acetate/acetic acid mixture
into 2.5ml (1.5 molar) hydrochloric acid.
The lower aqueous phase was
removed and spun at 2,500 x g to clear turbidity, protected from light
and read fluorometrically.
All readings were made within four hours of
extraction.
Fluore~cence
was measured on a Farrand Mark 1 Spectrof luoremeter
with a primary filter of 405nm and secondary filter of 600nm using a
Xenon lamp and lOnm slit widths.
Duplicate samples were run and if the
range exceeded 10% of the mean, further aliquots were analysed.
Protoporphyrin concentration was calculated from a standard curve
prepared from purified protoporphyrin material (Porphyrin Products,
Logan Utah 84321, U.S.A.).
Human blood pools were run as controls to
ensure reproducibility of the instrument.
Selecting a Maximum Acceptable Limit.
A maximum acceptable limit (M.A.L.) of 40 ugPb/lOOmls of whole blood
was adopted to identify swans with excess lead following Birkhead
(1982). 40ug/100mls is equivalent to 2.00umoles/ L. Since few
estimations of lead are accurate to 5%
(Chamberlain, 1985), a
conservative value of 2.20umoles/L is used here.
For corrected lead values, a mean value of haemoglobin for Mute
swans of 142g/L was used (after O'Halloran et al., (b) in press) and
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