Biochemical
Effects of Persea americana
(Avocado) and Dacryodes edulis (African
Pear) Extracts on Liver Function Test of Albino Wistar
Rats
Edokwe Chinelo*, Obidoa Onyechi, and Joshua Parker
Elijah
Department of Biochemistry, Faculty of Biological
Sciences, University of Nigeria, Nsukka, Enugu State,
Nigeria
ABSTRACT:
The liver function tests of the animals fed P. americana
showed that the enzyme activities of alanine aminotransferase (ALT) was 57.35 ± 4.40IU/L, aspartate aminotransferase 77.44
± 3.53IU/L and alkaline phosphatase 170.73 ± 6.52IU/L
while the enzyme activity of those fed D.
edulis was 45.57 ± 2.28IU/L AST, 68.26 ± 3.69IU/L
AST and 153.36 ± 19.08IU/L ALP. AST and ALT increased significantly (p<0.05)
in the sera of rats administered P. americana pulp compared with
those fed D. edulis.
However, no significant difference was observed (p>0.05) was observed in the
ALP activities of the three groups. The total cholesterol level of animals
administered D. edulis
(75.76 ± 5.37mg/dl) was lower compared with those administered P. americana
(115.75 ± 22.6mg/dl).
KEYWORDS: Coconut
(Cosos nucifera),
Calcium, Magnesium, Zinc.
INTRODUCTION:
Alanine aminotransferase (ALT),
formerly called serum glutamate-pyruvate transminase (SGPT), catalyses the transfer of α-amino
group from alanine to α-keto-glutarate
with the release of pyruvate and glutamate (Murray et al., 2003). Alanine
aminotransferase can also be found in several tissues
throughout the body, but the concentrations in the liver are considerably
higher than elsewhere. It is a cytosolic enzyme. Alanine aminotransferase is found
in high concentrations in the hepatocytes, and in
much smaller concentrations in other tissues such as kidney, heart, skeletal
muscle, pancreas, spleen and in erythrocytes and serum. There is more than one
form of alanine aminotransferase
in the body. The mitochondrial form is low in concentration and very unstable
as compared to the cytosolic form. The different electrophoretic components have been identified. They
include alanine glutamate transaminase
and alanine pyruvate transaminase. The former is very specific for alanine and glutamic acid,
whereas the latter is non-specific and has alanine
and pyruvate as principal substrates and can also act
on other amino acids though at a very low rate (Murray et al., 2003).
Aspartate aminotransferase
(AST), formerly known as glutamate-oxaloacetate transaminase (GOT) or serum glutamate–oxaloacetate
transaminase (SGOT), catalyses the transfer of the
α-amino group from aspartate to α-ketoglutarate with the release of oxaloacetate
and glutamate. Aspartate
aminotransferase is located in the cytosol and mitochondria of the liver cells. There are
individual iso–enzymes, and the main serum component
is from the cytosolic fraction. This enzyme is also
located in the cardiac muscle, skeletal muscle, brain, kidney, pancreas,
Spleen, erythrocytes and serum.
The hepatic mitochondrial cytosolic
AST isoenzymes are genetically distinct and different
in their amino acid composition, kinetic behaviour, electrophoretic mobility and
immunochemical properties. Isoelectric focusing shows
that mitochondrial isoenzymes from human liver exist
in a single form whereas the cytoplasmic isoenzymes have at least three sub-forms with similar
immunochemical behaviour (Nelson and Cox, 2000).
Alkaline
phosphatase is the name given to a group of enzymes
that catalyse the hydrolysis of phosphate esters in
alkaline pH. This enzyme is widely distributed in
human tissues, including liver, bone, placenta, intestine, kidney and
leukocytes. In the liver, the enzyme is mainly bound to canalicular
membranes (Nelson and Cox, 2000).
Liver
and bone isoenzymes are the major fractions of the
serum alkaline phosphatase in healthy adults. In
children and adolescents, where bone growth is active, the serum alkaline phosphatase may increase up to three fold and the bone isoenzymes become the major fraction. The placenta isoenzyme is prominent in pregnant women, particularly
during the third trimester. An intestinal component is often present in Lewis
antigen secretors of blood groups O and B, particularly after ingesting a fatty
meal (Nelson and Cox, 2000).Although the prime metabolic function of the
enzymes is not yet understood, the enzyme is closely associated with the
calcification process in bones. Alkaline phosphatase
displays considerable inter ad intra – tissue heterogeneity, but there are
rarely more than two or three forms in any one serum specimen. (Nelson and Cox, 2000).
Analysis
of some enzyme activities in blood serum gives valuable diagnostic information
for a number of disease conditions. Alanine aminotransferase (ALT; also called glutamate–pyruvate transaminase, GPT) and aspartate aminotransferase (AST;
also called glutamate–oxaloacetate transaminase, GOT) are important in the diagnosis of heart
and liver damage caused by heart attack, drug toxicity or infection. After a
heart attack, a variety of enzymes, including these aminotransferases,
leak from the injured heart cells into the blood stream. Measurements of the
blood serum concentration of the two aminotransferases
and alkaline phosphatase by SGPT, SGOT and alkaline phosphatase
tests and of another enzyme, creatine kinase and is the
first heart enzyme to appear in the blood after a heart attack; it also
disappears quickly from blood. AST is the next to appear and ALT follows later
(Nelson and Cox, 2000).
The
AST and ALT tests are also important in industrial medicine, to determine
whether people exposed to carbon tetrachloride, chloroform, or other industrial
solvents have suffered liver damage. Aminotransferases
are most useful in the monitoring of people exposed to these chemicals because
they are very active in liver and their activity can be detected in very small
amounts (Nelson and Cox, 2000).
Sterols
are structural lipids present in membranes of most eukaryotic cells. Their
characteristic structure is the steroid nucleus consisting of four fused rings,
three with six carbon and one with five. The steroid
nucleus is almost planar and is relatively rigid; the fused rings do not allow
rotation about C–C bonds. Cholesterol, the major sterol in animal tissues is amphipathic, having a polar head group (the hydroxyl group
at C-3) and a non– polar hydrocarbon body (the steroid nucleus and the
hydrocarbon side chain at C-17) about as long as a 16–carbon fatty acid in its
extended form. Similar sterols are found in other eukaryotes: stigmasterol in plants and ergosterol
in fungi, for example. Bacteria cannot synthesize sterols; a few bacteria
species however, can incorporate exogenous sterols into their membranes. The
sterols of all eukaryotes are synthesized from such simple five–carbon isoprene
subunits as are the fat–soluble vitamins, quinines and dolichols
(Nelson and Cox, 2000).
The
study was aimed at evaluating some nutritional and biochemical potential of P. Americana and D. edulis in rats using some liver enzyme
markers.
MATERIALS AND
METHODS:
Animals:- The experimental animals used for this study were
albino Wistar rats aged between 8 and 12 weeks old
within the weight range of 100g to 200g. The animals were obtained from the
animal house of the Veterinary Faculty of the University of Nigeria, Nsukka.
Plant Sample Materials:-
P.
americana
(Avocado pear) and D. edulis
(African pear) were obtained from Ogige market, in Nsukka, Enugu State. The two pears were identified by Mr.
Alfred Ozioko of Department of Botany, University of
Nigeria, Nsukka.
Chemicals and Reagents:-
All chemicals and biochemicals
used were purchased from Sigma chemicals, St Louis, USA and were of analytical
grade. Kits for evaluation of liver and kidney functions were products of Quimica Clinica Applicada (QCA), Spain. Also, the kit used for evaluation
of total cholesterol was purchased from Quimica Clinica Applicada (QCA), Spain.
Experimental Design:-
Fifteen (15) female albino Wistar rats were randomly distributed into three groups of
five rats each and housed in separate cages. The rats were acclimatized for a
period of seven days. They had free access to commercial poultry feed and water
throughout the duration of the experiment. The rats in group A were the control
and those in groups B and C were the test groups administered 20ml/kg body
weight each of P. americana (Avocado pear) and
D. edulis (African pear) pulp respectively
which was prepared by dissolving 5g pear pulp in 95ml water to form stock
concentration daily. The experiment lasted for fourteen days. The animals were
weighed at the beginning and end of the feeding. On the 15th day,
the animals were sacrificed, kidney, liver, heart and spleen weights measured
and blood samples collected for some biochemical analysis using ocular
puncture.
Assay of Alanine
aminotransferase (ALT) activity:
The
activity of (ALT) was determined by the Reitman-Frankel
colorimetric method (1957) for in vitro determination of GPT/ALT in serum using
a Quimica Clinica Applicada (QCA) test kit.
Assay of Aspartate aminotransferase (AST) activity:
GOT (AST) determination by the Reitman – Frankel colorimetric method (1957) for in vitro
determination of GOT/AST in serum using a Quimica Clinica Applicada (QCA) test kit.
Assay of Alkaline phosphatase (ALP) activity:
Phenolphthalein monophosphate method (Klein et al., 1960) for the in vitro determination of alkaline phosphatase in serum using Quimica
Clinica Applicada (QCA)
test kit.
Total cholesterol determination:
Enzymatic
colorimetric test (CHOD-PAP Method), according to the method of Allain et al.
(1974) was used for the in vitro
determination of serum cholesterol using Quimica Clinica Applicada (QCA)
cholesterol test kit.
RESULTS:
Effect of Persea americana (Avocado )
and Dacryodes edulis
(African pear) on the Alanine aminotransferase
(ALT)
The
result in Fig. 1 showed that the ALT activity of the test group administered P. americana
was not significantly different (p>0.05) compared with the control group.
There was a significant difference (p<0.05) in the test group administered D. edulis
compared with the control group.
There was also a significant decrease (p<0.05) in ALT in animals
administered D. edulis compared to those administered (p.o) P. americana.
Fig. 1: Effect
of Persea americana (Avocado ) and Dacryodes edulis (African pear) on the alanine
aminotransferase (ALT) activity of experimental rats.
Effect of Persea americana (Avocado )
and Dacryodes edulis
(African pear) on the Aspartate aminotransferase
(ALT)
The
result in Fig. 2 showed that the rats fed P.
americana had a higher
AST activity and the value differed significantly (p<0.05) from the control
group. There was no significant difference (p>0.05) in the group
administered (p.o) D. edulis compared with the control
group. The AST activity showed a significant difference (p<0.05) in the test
group fed P. americana compared with those fed D. edulis.
Effect of Persea americana (Avocado )
and Dacryodes edulis
(African pear) on the Alkaline phosphatase (ALP)
The
ALP activity in Fig. 3 shows that there was a significant decrease (p<0.05)
in rats fed D. edulis
(African pear) compared with the control group. The ALP activity of the control
group showed non-significant difference (p>0.05) compared with test group
fed P. americana
(Avoado) . There was also
non-significant difference (p>0.05) in the ALP activity of those fed D. edulis
(African pear) compared with those fed P.
americana (Avocado).
Fig. 2: Effect
of Persea americana
(Avocado) and Dacryodes
edulis (African pear) on the aspartate
aminotransferase (AST) activity of experimental rats.
DISCUSSION:
As
shown in the result, the activity of alanine aminotransferase increased significantly (p<0.05) in the
group administered (p.o) P. americana
when compared with those fed D. edulis.
The decreased activities of ALT activity of rats fed D. edulis and those fed P. americana
when compared with those of the control suggest that the test diets did not
adversely affect liver functioning. The slight increase in ALT of the group
administered P. americana could have been from other sources
other than the liver. Also, the minor elevation of AST activity in rats fed P. americana
could have been from other sources than the liver; although damage is
considered for elevations ranging from 2 times and above the upper limit of the
normal level (Jaeger and Hedegaard, 2003). ALT
activity is higher than the AST when a liver damage is present (Song et al., 2004). But when AST activities
are higher than the ALT, cirrhosis is generally present. The most commonly used
markers of hepatocytic injury are aspartate
aminotransferase and alanine
aminotransferase. While ALT is cytosolic,
AST has both cytosolic and mitochondrial forms
(Johnston, 1999). AST is present in large amounts in the liver, heart, skeletal
muscle, brain and red blood cells. It is therefore less specific for liver
disease because it can be elevated also in myocardial infarction, myopathies, muscular disease (musclar
dystrophy, rhabdomyolisis) or trauma. While ALT is
present in large concentration in liver and in lesser amount in kidney, heart
and skeletal muscle. It is therefore more specific for liver disease than AST
(Song et al., 2004). In this study, the AST activity differed
significantly (p<0.05) in the group administered P. americana when
compared with those administered D. edulis.
Fig. 3: Effect
of Persea americana
(Avocado) and Dacryodes
edulis (African pear) on the alkaline phosphatase (ALP) activity of experimental rats.
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Received on 24.02.2010
Accepted on 12.02.2010
© A &V Publication all right reserved
Research J. Science and Tech. 2(2): March –April. 2010: 34-37