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

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Chapter | 13 Hepatic Function
TABLE 13-2 Serum Sorbitol (Iditol) Dehydrogenase
(SOH) Activity of Normal Animals
Species U/liter Reference
Dog 28 20 Zinkl et al . (1971)
5.5–18 Noonan and Meyer (1979)
1–9 Abdelkader and Hauge (1986)
0–6 Keller (1981)
10 3 Anwer et al . (1976)
Pony 14.7 3.6 Anwer et al . (1976)
Calf 14.7 1.3 Anwer et al . (1976)
Cow 4.3–15.4 Putnam et al . (1986)
Sheep 16.5 1.5 Anwer et al. (1986)
7.9 2.3 Alemu et al . (1977)
type II is a mitochondrial enzyme that is expressed in most
tissues including the kidney ( Morris et al., 1997 ; Shi et al.,
1998 ). Type II arginase appears to control the availability
of the arginine used for nitric oxide synthesis (Gotoh and
Mori, 1999) and has an important role in the synthesis of
ornithine, which is a precursor of polyamines, glutamate,
and proline ( Jenkinson et al., 1996 ).
Because the activity of arginase in liver is higher than
in other organs ( Aminlari and Vaseghi, 1992 ; Aminlari
et al., 2007 ), elevations in serum arginase activity have
been considered to be liver specific ( Cornelius et al., 1963 ;
Dittrich et al., 1974 ) and a convenient assay has been validated
for measurement ( Mia and Koger, 1978 ). Following
acute liver injury, serum arginase increases and then
decreases rapidly ( Aminlari et al., 1994 ; Cornelius et al.,
1963 ). Sustained elevation in serum arginase activity suggests
an unfavorable prognosis. Elevations in serum arginase
have been demonstrated in naturally occurring liver
disease of horses (Wolf et al., 1967) , cattle, sheep ( Ross,
1966 ), goats, and dogs ( Harvey and Hoe, 1971 ). When
serum arginase and GGT activities are measured simultaneously,
their respective specificities for hepatocellular
injury and cholestasis can be useful ( Noonan and Meyer,
1979 ).
4 . Glutamate Dehydrogenase
GD is a mitochondrial enzyme with a key role in the detoxification
of ammonia. GD serves as an ammonia scavenger
by catalyzing the amination of α -ketoglutarate to
form glutamate. Glutamate produced by GD is converted
by mitochondrial AST to aspartate, which is urea synthesis.
Glutamate also is used in the mitochondrial synthesis
of N-acetylglutamate, the allosteric activator of carbamoyl
phosphate synthase that is the enzyme responsible for the
first step in urea synthesis ( Caldovic and Tuchman, 2003 ;
Caldovic et al., 2006 ; Nissim et al., 2003 ).
TABLE 13-3 Serum Glutamic Dehydrogenase (GD)
Activity of Normal Animals
Species U/liter Reference
Dog 0–9 Abdelkader and Hauge (1986)
1–6 Keller (1981)
0–1.2 Freedland et al . (1965)
Sheep 0–9 Alemu et al . (1977)
2.6 1.0 Harvey and Obeid (1974)
Goat 3.4 0.9 Harvey and Obeid (1974)
GD has been shown to be useful in the assessment of
hepatic necrosis in sheep, goats, and cattle ( Table 13-3 ).
GD activity is highly concentrated in ovine and bovine liver
( Keller, 1971 ) as well as in the liver of other domestic species
( Keller et al., 1985 ). Elevated GD activity has been
reported in ruminants with hepatic necrosis ( Fowler, 1971 ),
associated with parturition ( Treacher and Collis, 1977 ) and
with obstruction of the bile duct ( Ford and Gopinath, 1976 ).
5 . Ornithine Carbamoyltransferase
OCT catalyzes the reaction between ornithine and carbamoyl
phosphate forming citrulline and inorganic phosphate.
The enzyme is located in mitochondria and functions as a
part of the urea cycle. OCT is considered a liver-specific
enzyme for the detection of hepatocellular necrosis in
domestic species ( Treacher and Sansom, 1969 ). Nearly all
OCT activity is confined to the liver of cattle ( Treacher and
Collis, 1977 ) and of pigs ( Dittrich et al., 1974 ). OCT and
ALT are similar in sensitivity as diagnostic tests for hepatic
necrosis in the dog. A similar association of OCT with
hepatocellular injury has been observed in swine ( Wilson
et al., 1972 ), and Markiewicz et al. (1975) have reported
that serum OCT activity is correlated with the severity of
hepatic fascioliasis in cattle.
6 . Serum Alkaline Phosphatase
The APs are a group of zinc metalloenzymes that are present
in most tissues. High concentrations are found in the
intestine, kidney, bone, and liver. Light and electron microscopic
studies have demonstrated that alkaline phosphatase
activity is highest on the absorptive or secretory surfaces
of cells ( Kaplan, 1972 ). Within liver cells, alkaline phosphatase
is bound to membranes and AP activity sediments
with the microsomal and plasma membrane fractions
( Emmelot et al., 1964 ).
The actual physiological functions of alkaline phosphatase
are not fully understood. Localization of the enzyme to
cell surfaces known to be responsible for active absorption
or secretion suggests a role in membrane transport. There
is evidence suggesting that the alkaline phosphatase of