The effect of pH on alkaline phosphatase activity in serum of the rat and other species.

Contrary to other species, optimum pH of alkaline phosphatase (alk.P.) activity was 9.6 in fed male rats of all age groups studies. In 3- or 6-week-old fasted rats, the optimum pH shifted to 9.8-10.0. This shifting of pH did not occur in 11-week-old rats. Heating to 56 degrees C for 10 min shifted the optimum pH in 3-week-old rats to 9.0, in 6-week-old rats to 9.0-9.4, but no change occurred in 11-week-old rats. In other species (mouse, rabbit, and man), the optimum pH was 10.0-10.2, and was not influenced by fasting or heating.