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

II. Physiology of Adrenocortical Hormones
607
FIGURE 19-2 Biosynthetic pathways
for adrenal steroid production. Numbers
by arrows denote specific enzymes: 1
CYP11A1; 2 CYP17; 3 3 β-HSD;
4 CYP21; 5 CYP11B1;
6 CYP11B2.
corticosterone ratios to range from about 3 to 7. In another
study, ratios of secretion rates were found ranging from
1.2 to 2.7 and corticosterone/aldosterone secretion ratios
between 7 and 25 ( Dor et al ., 1973 ). With HPLC analysis
in peripheral blood of ACTH-stimulated dogs, the
cortisol/corticosterone ratios ranged from 2.4 to 9.7 with
a mean of 5.0 ( Lothrop and Oliver, 1984 ). In addition to
glucocorticoids and aldosterone, the adrenal vein blood of
dogs and pigs contains androstenedione, 11-hydroxyandrostenedione,
androsterone, pregnenolone, progesterone, and
11-hydroxyprogesterone ( Heap et al ., 1966 ; Holzbauer and
Newport, 1969 ), as well as very small amounts of estradiol
and estrone ( Dor et al ., 1973 ).
In cats, the cortisol/corticosterone ratio has been estimated
to range from 1.6 to 12.4, whereas in kittens the
ratio is less than unity ( Ilett and Lockett, 1969 ). In the