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

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Chapter | 21 Clinical Reproductive Endocrinology
Mean progesterone percentage
120
100
80
120
100
80
120
100
80
100
80
60
40
20
Dog
Pig
Horse
Bovine
0 2 4 6 24 48 120
Incubation time (hours)
FIGURE 21-10 Mean (and SD) plasma progesterone percentage after
storage of heparinized whole blood from four dogs, four pigs, four horses,
and eight cows at 20°C ( • ) and at 4°C ( ° ). The initial progesterone value
at time 0 has arbitrarily been set as 100% ( Oltner and Edqvist, 1982 ).
in progesterone, the lower the temperature of storage, the
slower is the rate of progesterone decline ( Fig. 21-10 ).
The enzymes responsible for the progesterone conversion
are present in the red blood cells; harvesting serum or
plasma as soon as possible after the collection of the sample
prevents the metabolism of progesterone ( Vahdat et al. ,
1979 ). If this cannot be done within half an hour, the sample
should be put on ice to retard the enzymatic processes.
A decline in progesterone concentrations also occurs
in stored whole blood from the ewe ( Van der Molen and
Groen, 1968 ; Wiseman et al. , 1983 ), although the decline
is not as rapid and pronounced as in the cow. In the female
goat, on the other hand, no significant decrease in whole
blood progesterone was found during storage at room temperature
for 24 h ( Navarro et al. , 1990 ). Some decline in
progesterone also seems to occur during storage of equine
whole blood ( Fig. 21-10 ). For other domestic animals dealt
with here, no major effects of storage on progesterone concentrations
have been reported.
Storage of bovine whole blood also results in significant
decreases of 17-keto-androgens (e.g., androstenedione,
dehydroepiandrosterone) and 17-keto-estrogens (e.g.,
estrone) because 17 α -hydroxysteroid dehydrogenase present
in red blood cells converts the steroids to epitestosterone
and estradiol-17 α , respectively ( Choi et al. , 1989 ).
Concentrations of testosterone and estradiol-17 β are not
influenced when storing whole bovine blood over 24 h at
20°C ( Choi et al. , 1989 ).
Plasma or serum samples can be stored frozen for long
periods of time without a significant loss in reproductive
hormone concentration. Sample handling procedures from
blood collection to the freezing of serum or plasma should
be standardized for each species and hormone determined.
2 . Milk
Milk samples for progesterone analysis can be preserved
with sodium azide, potassium dichromate, or thimerosal
Progesterone nmol/l
90
80
70
60
50
40
30
FIGURE 21-11 Hourly changes in whole-milk
concentrations of progesterone due to the variation
in fat content during 24 h, mean and SE of 12 cows
( Garcia and Edqvist, 1990 ).
20
10
0
05 07 09 11 13 15 17 19 21 23 01 03 05
Clock time