Observations on the heat stability and electrophoretic pattern of alkaline phosphatases extracted from various...

Various tissues were extracted with either normal saline or heat inactivated serum (HIS) and the heat stability and electrophoretic migration of the alkaline phosphatase enzymes (AP) of the extracts were compared to the heat stability and electrophoretic properties of serum AP. The electrophoretic pattern of HIS extracts of liver and bone differed from that of saline extracts but the pattern was unaffected if HIS was added to the saline extracts. The heat stabilities of the tissue AP also differed depending on whether they were extracted with saline or HIS. However, serum AP heat stability can help differentiate between liver and bone disease. It is concluded that the comparison of serum and tissue AP heat stabilities or the comparison of serum and tissue AP electrophoretic patterns as criteria for identification of the tissue source of the serum enzyme may be misleading since both these parameters vary, depending on the medium used for extracting the tissue and the extract(s) may contain a mixture of enzymes different from that in serum. It is further concluded from the electrophoretic studies on tissue AP that the increased serum AP in patients with hepatobiliary disease was unlikely to be due to regurgitation of bile but due to increased synthesis and release of alpha 1 and alpha 2 AP isoenzymes from liver, bile ducts or gall bladder. In patients with bone disease the increased serum AP is derived from bone. The source of the serum AP of "normal" subjects may be either liver or vascular tissue or both.