Serum Chemestry Tests
Increased ALT indicates hepatic cell damage or necrosis
Alanine transferase (ALT), formerly known as SGPT, is present in large quantities in the cytoplasm of canine and feline hepatocytes. This enzyme enters the blood when liver cells are damaged or destroyed and circulates for a few days.
This enzyme is a sensitive indicator of active liver damage but does not indicate the cause or reversibility of the damage. Increased serum ALT activity indicates recent or ongoing liver cell damage. An increase of at least three times normal indicates significant liver damage within the previous 2 to 5 days.
Albumin Increased albumin suggests dehydration malnutrition malabsorption, enteritis, and glomerulonephritis causeI decreased albumin. Severe dehydration often increases serum albumin levels.
Albumin is a serum protein that affects osmotic pressure, binds calcium, and transports fatty acids and many drugs.Starvation, parasitism, chronic malabsorptive disease, chronic liver disease, exudative enteritis, and glornerulonephritis decrease serum albumin levels. Hypoalbuminemia with normal serum globulin levels suggests decreased albumin production, increased loss, or sequestration. If both albumin and globulin levels are low, hemorrhage, exudation, and dilution are likely causes.
Alkaline phosphatase (AP) is found in both liver and bone.Elevated AP activity in the serum indicates increased production by the liver parenchyma, bile ducts, and growing bone or decreased excretion in bile and urine. Elevated AP activity does not suggest liver or bone necrosis.
Serum AP activity increases after an episode of acute pancreatitis because of secondary cholangitis. It also increases if liver disease causes a disruption of hepatobiliary architecture with local impairment of bile flow.
Cats have less AP than dogs and the kidneys rapidly excrete slight excesses. Any increased AP activity in cats is significant and suggests cholestasis.
Normal values in puppies and kittens are higher than in adults because of active bone growth. Diseases causing bone remodeling in adults cause slight elevations of less than two times normal.
Persistence of AP activity unrelated to continued disease might be due to decreased clearance secondary to diseases such as renal failure, cirrhosis, or the formation of macroenzymes.Alpha-2 Acid Glycoprotein (AGP)
Increased AGP is a very early indicator of diseaseAlpha-2 acid glycoprotein (AGP) is an acute phase protein manufactured in the liver and found in the blood. Detection of elevated levels of AGP indicate's illness or other stressors even though an animal appears clinically normal. AGP indicates disease before antibodies are created by the immune system and before clinical symptoms are apparent. AGP is elevated by inflammation, infectious diseases, surgery, malignant tumors, autoimmune diseases, liver cirrhoses, and with all types of stress in general.
The AGP test is species specific and is available in kit form. It can be used as a prognostic indicator to detect subclinical disease and changes in homeostasis and to monitor immune system function, chemotherapy, and vaccine efficacy. In monitoring cancer therapy, continued high levels of AGP where the level was initially high suggests that treatment is not working or not appropriate. Levels above 1000 mg/ml of serum indicate a poor prognosis, especially if subsequent measurements show increasing levels.
Alpha Glutathione S-Transferase (GST)
Increased GST indicates early hepatocyte injuryAlpha glutathione S-transferase (GST) is a superior marker of hepatocyte injury from toxicity; ischemia, and other liver injury. It is unique to hepatocytes, found in high concentrations, and is readily released in response to injury. It comprises 5% of the soluble protein of hepatocytes. Its rapid release into and removal from the circulation provides immediate information regarding liver status. It is a valuable tool in research evaluation of liver damage.
Protein catabolism, gluconeogenesis, and increased insulin activity reduce serum levels of branched-chain amino acids. Hepatic insufficiency from portosystemic shunts or liver fibrosis (cirrhosis) increases serum levels of aromatic amino acids. The ratio of branched-chain to aromatic amino acids is termed the amino acid (AA) ratio.
aromatic AA increase with hepatic insufficiency
The AA ratio is decreased with hepatic encephalopathy. CNS signs occur because increased levels of aromatic amino acids increase production of inhibitory neurotransmitters, while decreased levels of branched-chain amino acids decrease production of stimulatory neurotransmitters.Normal branched -chain: aromatic AA ratio >3
Increased ammonia indicates hepatic-insufficiencyIncreased baseline blood ammonia levels or persistently high blood ammonia levels after oral administration of ammonium chloride (available as a urine acidifier) indicate hepatic insufficiency. This test is helpful in evaluating animals with chronic weight loss, abnormal CNS signs, and a small liver. Abnormalities correlate with serum bile acid assays. Congenital and acquired hepatic shunts, bile duct obstruction, cholangiohepatitis, and cirrhosis increase blood ammonia levels.