Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter | 28 Avian Clinical Biochemistry
50
80
44
68
Serum total protein (g/l)
38
32
y 1.74 1.01 X
Refractomter
56
44
26
32
20
20 26 32 38 44 50
Plasma total protein (g/l)
FIGURE 28-4 Relation between plasma and serum total protein by
biuret method in racing pigeons (n 50; g/l). From Lumeij and Maclean
(1996) .
and reduced hematocrit may contribute to the maintenance
of blood pressure, whereas the decreased hematocrit may
enhance blood flow to metabolically active tissues.
The absence of changes in plasma corticosterone concentrations
during the shorter flights can be considered as
an absence of stress under the circumstances studied.
IV . PLASMA PROTEINS
A . Introduction
Plasma proteins are important complementary constituents
in the diagnosis of gastrointestinal, hepatic, renal, or infectious
diseases. Determination of plasma proteins seldom
leads to a specific diagnosis (e.g., monoclonal gammopathies)
but will help the clinician to evaluate the nature,
severity, and progress of a disease.
B . Plasma versus Serum
In pigeons, the concentration of total protein (TP) in plasma
is about 1.5 g/L higher than in serum, because the former
also contains fibrinogen: TP serum 1.7 1.01 TP plasma
( Fig. 28-4 ). According to Lumeij and McLean (1996), the
correlation is highly significant ( p 0.000001; R 0.99;
n 50). Differences between plasma and serum were discussed
in Section II.B . When plasma rather than serum is
used, recognition of elevated fibrinogen concentration can
be seen in the protein electrophoresis and is reflected by
elevation of the acute phase ( α or β ) proteins ( Roman et al .,
2005 ). See also Section XII.C.6.
20
20 32 44 56 68 80
Biuret method
FIGURE 28-5 Relation between plasma total protein concentration by
biuret method and two types of refractometers in pigeons (g/L; n 58).
Symbols: , temperature compensated refractometer (y 16.38 1.93 X;
r 0.89); , nontemperature compensated refractometer (y 25.88
2.06 X; r 0.89). From Lumeij and McLean (1996).
C . Physiological Variation in Female Birds
In female birds, a considerable increase in plasma total
protein concentration occurs just before egg laying because
of an estrogen-induced increase in the globulin fractions
( Griminger, 1976 ). The proteins are the yolk precursors
(e.g., vitellogenin and lipoproteins), which are synthesized
in the liver and transported to the ovary, where they are
incorporated in the oocyte ( Griffin et al. , 1984 ).
D . Refractometry versus the Biuret Method
Lumeij and De Bruijne (1985b) demonstrated that the
refractometric method is unreliable for use in avian blood
and therefore this method should not be used in avian
practice. The refractometric method consistently yields
higher values when compared to total protein concentrations
determined with the biuret method, and the correlation
coefficient between these two methods is low. One
study suggested that only temperature compensated refractometers
are reliable ( Andreasen et al. , 1989 ). In another
study in our laboratory (Lumeij and McLean, 1996), using
plasma and serum of 58 pigeons, two types of refractometers
were compared with the biuret method. Neither instrument
proved to give an accurate measurement of plasma
total protein. Both refractometers gave considerably higher
values than the biuret method, with the temperature compensated
instrument being consistently higher in readings
than the nontemperature compensated one ( Fig. 28-5 ).
It was concluded that a species- and refractometer-specific
conversion factor must be applied before refractometric