Rat serum alkaline phosphatase electrophoretic fractions: variations with feeding, starvation and cellulose fibre ingestion

The effect of feeding, starvation and fibre ingestion on alkaline phosphata se (ALP) activity (E.C. 3.1.3.1) was studied in Wistar rat serum. Using ide ntical assay conditions for total ALP activity determination and for electr ophoretic ALP isoenzymes/fractions activity calculation, alpha- and beta-na phthyl phosphates and p-nitrophenyl phosphate were used as substrates and 2 -amino-2-methyl-1-propanol/HCl was used as buffer, respectively. Total acti vity with beta-naphthyl phosphate was significantly higher than with alpha- naphthyl phosphate and p-nitrophenyl phosphate; with alpha-naphthyl phospha te it was significantly higher than with p-nitrophenyl phosphate. With all substrates, fed animals had significantly higher total activity than starvi ng ones. Electrophoresis allowed the separation of two fractions. The secon d fraction activity was significantly higher in the fed group than in the s tarving ones, irrespective of the substrate used. Starving animals with fib re showed higher values of this fraction than starving animals without fibr e, the difference reaching statistical significance with a-naphthyl phospha te. The first fraction predominated in both starved groups and the second i n the fed group. The second fraction was identified as intestinal ALP. We c onclude that the mechanical stimulation of the digestive tract: appears to influence the passage of intestinal ALP to serum. The experimental conditio ns used enable quantification of electrophoretic fractions based on total a ctivity. Activity depends on the substrate used.