Simple, cost-effective isoenzyme quantitation within
Alkaline phosphatase (ALP) is an enzyme which catalyses the hydrolysis of phosphate esters at alkaline pH. The greatest concentrations of ALP are found in the liver, bone, intestine and placenta. However, practically every body tissue contains at least a small amount of ALP. Each source of ALP produces one predominant isoenzyme and the tissue source of elevated ALP in serum can be determined by identifying the isoenzyme type.
Alkaline phosphatase is a relatively common test but has long since been neglected in general laboratory practice with a preference to send away. This article examines what the test is and why clinicians can easily and cost-effectively bring it back into routine laboratory use. The isoenzymes of ALP differ in their physiochemical and electrophoretic properties and, by taking advantage of these differences, the individual isoenzymes can be identified.1
The Helena Biosciences Europe Alkaline Phosphatase Isoenzyme kit separates and quantifies Alkaline Phosphatase Isoenzymes by agarose gel electrophoresis.
The Helena Biosciences Europe Alkaline Phosphatase Isoenzyme kit detects liver, bone, parathyroid and intestinal isoenzymes in serum for use in the diagnosis and treatment of:
Liver disorders such as:
Bone disorders such as:
Parathyroid disorders such as:
Intestinal disorders such as:
The system also separates the intestinal isoenzyme into 3 distinct bands.
The test can be performed on all three Helena Biosciences Europe systems (SAS-MX, SAS-1+ and SAS-3) using fresh serum and utilising differences in the response of the isoenzymes to neuraminidase and a detergent in the gel to separate the different isoenzymes.2
The primary importance of measuring alkaline phosphatase is to check the possibility of bone disease or liver disease. Since the mucosal cells that line the bile system of the liver are the source of alkaline phosphatase, the free flow of bile through the liver and down into the biliary tract and gallbladder are responsible for maintaining the proper level of this enzyme in the blood. When the liver, bile ducts or gallbladder system are not functioning properly or are blocked, this enzyme is not excreted through the bile and alkaline phosphatase is released into the blood stream. Thus the serum alkaline phosphatase is a measure of the integrity of the hepatobiliary system and the flow of bile into the small intestine.3
In addition to liver, bile duct, or gallbladder dysfunction, an elevated serum alkaline phosphatase can be due to rapid growth of bone since it is produced by bone forming cells called osteoblasts. The relationship of alkalinity to bone development warrants further discussion because it plays a major role in the prevention and reversal of osteoporosis.3
The Alkaline Phosphatase Isoenzyme procedure is a high resolution method, and the isoenzyme migrations differ from those seen in conventional isoenzyme electrophoretic methods. Taking advantage of this results in greater separation of the liver and bone isoenzymes and allows for simple result interpretation.
Serum from normal individuals may contain small amounts of intestinal, liver and bone ALP.
Liver: Has the most anodic migration of all bands. Liver is the enzyme most frequently elevated when total ALP levels are elevated.4,5
Bone/Placental: Next to the liver band running more cathodally is the bone/placental band. This band has a characteristic square shape as opposed to the more oblong shape of the electrophoretic bands.
Macrohepatic: Running cathodally to the bone band is the Macrohepatic (fast liver) band. Macrohepatic ALP has been isolated in cases of metastatic carcinoma to the liver and has been suggested as a diagnostic tool in identifying such cases.6
Intestinal: The intestinal bands run more cathodal to the Macrohepatic band. An appearance of up to 3 bands is common in samples from non fasting patients.
Alkaline Phosphatase Isoenzymes
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