Clinical chemistry
-
Continuous monitoring of heat denaturation of a mixture of alkaline phosphatase isoenzymes at 60 degrees C and pH 7.5 permits the simultaneous direct identification and quantitation of three isoenzymes: the placental isoenzyme, the L-phenylalanine-sensitive intestinal isoenzyme, and the liver isoenzyme (hepatocytic). The isoenzyme that is principally of bone origin cannot be identified as such without the help of other diagnostic aids and the patient's medical history. All human tissues contain alkaline phosphatase, many organs more than one of the isoenzymes. ⋯ Liver alkaline phosphatase activity increases in the blood early in liver disease, before most liver tests show abnormalities. The other major isoenzyme of normal serum probably represents a mixture of isoenzymes from bone and reticulo-endothelial and vascular tissues, which all contain the same "very heat-labile" alkaline phosphatase. Cord blood and children's sera contain mostly this very heat-labile isoenzyme.