Abstract
The optimum pH of serum alkaline phosphatase (alk. P., EC 3.1.3.1) was investigated in adult male rats, mice and rabbits after fasting or after the induction of cholestasis by a single oral dose of 200 mg/kg alpha-naphthylisothiocyanate (ANIT). The nature of serum alk.P. was also studied with the inhibitory effects of three L-amino acids (L-phenylalanine, L-homoarginine and L-cystine) and by electrophoresis. In the rat, fasting as well as ANIT-treatment shifted the optimum pH of alk.P. from 9.4 to 10.0 due to a decrease in intestinal isoenzymes or due to newly appeared liver isoenzymes, while no shifting occurred in mouse and rabbit.
