Alkaline phosphatase and its isoenzymes in the tissues and sera of normal dogs.

The total alkaline phosphatase (AP) activity and the pattern of its isoenzymes were studied in the tissues and sera of normal adult dogs. Small intestine mucosa showed the greatest total AP activity followed by kidney, bone, pancreas, liver, lung, skeletal muscle and heart muscle. After separation by agarose gel electrophoresis, each tissue showed only one isoenzyme except lung which showed two. The tissue isoenzymes, in decreasing order of migration distance towards the anode, were as follows: fast lung isoenzyme, liver or slow lung isoenzyme, the group consisting of skeletal muscle, bone, small intestine and pancreas isoenzymes and, finally, the kidney isoenzyme. Two isoenzymes occurred in serum. The major band corresponded to liver and the slow lung isoenzyme, while the minor band was considered to be the corticosteroid-induced isoenzyme, previously thought to be absent from normal serum. The AP isoenzyme patterns in lung and skeletal muscle and the presence of an isoenzyme migrating an identical distance to the corticosteroid-induced isoenzyme do not appear to have been reported before in normal dogs.