Seasonal variations of K+-p-nitrophenyl phosphatase activity in the epidermis of the crested newt: A quantitative and ultrastructural study

The seasonal distribution of K + -p-nitrophenyl phosphatase, an enzyme involved in osmoregulation, was determined cytochemically in the skin of the crested newt. Microdensitometric measurements of the final reaction product of the enzyme showed a greater activity in the upper layers of the epidermis (except for the horny layer), and higher activities during the terrestrial phase (in the summer) compared to the aquatic phase (in the winter).