ISOFORMS OF ALKALINE-PHOSPHATASE DETERMINED BY ISOELECTRIC-FOCUSING IN PATIENTS WITH CHRONIC LIVER DISORDERS

Fractionation of alkaline phosphatase isoenzymes and isoforms by isoel ectric focusing is a simple procedure that resolves up to 17 fractions having alkaline phosphatase activity. The fractions are stable at 4 d egrees C, and undergo only slight changes during repeated freeze-thaw cycles. Petreatment with phospholipase-C or sialidase changes the isoe lectric focusing patterns of alkaline phosphatase in serum; we recomme nd they not be used owing to the loss of information. We found that th e alkaline phosphatase fractions provide diagnostic information in add ition to that given by the common liver-function tests in patients wit h chronic liver diseases. Primary biliary cirrhosis and primary sclero sing cholangitis showed similar biochemical changes, but they are very different from alcoholic cirrhosis based on the common liver-function tests and the alkaline phosphatase isoform patterns obtained by isoel ectric focusing. Analysis of the laboratory data using neural networks has some limited use in distinguishing chronic and chronic-active hep atitis of any cause. We have confirmed the tissue assignments made by Griffiths (Frog Clin Biochem 1989; 8:63-74) for the alkaline phosphata se fractions in liver as obtained by isoelectric focusing: Fractions l a and Ib show a strong correlation with biliary diseases, and fraction s 2, 3, and 4 show consistent increases in patients with primary disor ders of hepatocytes; these fractions have good sensitivity for hepatoc yte injury, but their specificity is limited. Fraction 10 may be a mar ker of activated T-lymphocytes; it was abnormal in most of our patient s suggesting that it is a sensitive but non-specific test. Analysis of alkaline phosphatase by isoelectric focusing deserves further evaluat ion, because it may facilitate the diagnosis of certain chronic liver disorders and could be a supplement to the biopsy.