Isoenzymes of canine plasma alkaline phosphatase: an investigation using isoelectric focusing and related to diagnosis.

The isoenzymes of canine alkaline phosphatase have been separated by isoelectric focusing on agarose gels. Alkaline phosphatase from normal tissue extracts gave heterogeneous focusing patterns with the following isoelectric points: liver pH 4.3, bone pH 4.0 to 4.9, kidney pH 4.4 to 4.7 and intestine pH 3.6 to 4.6. Plasma alkaline phosphatase isoenzymes were examined in 123 dogs with activities at least twice the normal maximum. The isoenzymes from these plasma samples had multiple bands at pH 4.3 to 4.6 but in 67 per cent of all cases, the predominant isoenzyme, named isoenzyme A, was a single band of isoelectric point pH 3.5. Isoenzyme A occurred in all dogs with diabetes mellitus or Cushing's syndrome and in 93 per cent of animals receiving steroid therapy. Increased activities of the pH 4.3 to 4.6 isoenzymes were more likely to occur in cases of hepatic degeneration.