Serum alkaline phosphatase isoenzymes in laboratory beagle dogs detected by polyacrylamide-gel disk electrophoresis

Serum alkaline phosphatase (ALP) activity is frequently measured in toxicity studies. Itoh et al. (2002) reported that a commercially available polyacrylamide-gel (PAG) disk electrophoresis kit used in humans (AlkPhor System, Jokoh Co., Ltd., Tokyo, Japan) for identifying serum ALP isoenzymes was useful for veterinary clinicopathological diagnosis in mongrel dogs. In the present study, based on the report of Itoh et al. (2002), we tried to expand the application range of this kit to laboratory beagle dogs which are commonly used in toxicity studies. In order to identify the origin of each ALP isoenzyme, tissue ALP extracts from the liver, bone and small intestine and serum samples were treated with neuraminidase, anti-small intestinal ALP antibody, ALP inhibitor levamisole and/or wheat germ agglutinin (WGA). The main serum ALP isoenzymes in 5-month-old intact beagle dogs were bone-derived (bone and atypical ALP: corresponding to human variant bone ALP) and they tended to decrease with age. However, liver-derived ALP isoenzyme greatly increased in the serum of cholestasis model dogs. The cholestasis model dogs also had a large molecular ALP detected in the resolving gel. This ALP could be originated from intestinal ALP or corticosteroid-induced ALP (CALP), because the activity remained even after levamisole inhibition. CALP was observed in intact laboratory beagle dogs with individual differences. These results suggest that the present method is a useful tool for detecting serum ALP isoenzymes in laboratory beagle dogs and concomitant levamisole inhibition with another gel is applicable for the evaluation of organ toxicity.

Age-dependent changes in the activity of serum alkaline phosphatase in laboratory beagle dogs

In order to prepare background data for toxicity studies, serum alkaline phosphatase activity in a total of 5,242 male and female beagle dogs was surveyed for the sequence of changes in activity through aging. About 95% of the beagle dogs surveyed were 5 to 12 months of age, corresponding with the age usually employed in toxicity studies. Serum alkaline phosphatase (ALP) activity, about 460 IU/l at 5 months of age, steadily decreased and reached a level about one third of that (about 160 IU/l) at 12 months of age, and remained unchanged thereafter. The above findings were essentially the same irrespective of sex and breeding colony. The present results are useful information in the evaluation of blood chemistry data in toxicity studies.