The degree of phosphorylation of intestinal brush border membrane proteins in an adult amphibian, Rana esulenta, was researched under various experimental conditions. The brush border protein phosphorylation rate rapidly increases during incubation in a medium containing ATP. On the contrary, this phosphorylation rate is significantly reduced by the presence of L-lysine. The brush border membrane proteins were identified. Electrophoresis followed by an radioautography demonstrates the existence of a very phosphorylated protein, which could be the monomer of alkaline phosphatase (molecular weight: 86 kDa). The phosphorylation of this protein is partially inhibited by L-lysine. From the metamorphosis, the intestine becomes the main organ involved with calcium absorption. In adult Rana esculenta, the correlation between the degree of phosphorylation of the intestinal brush border membrane proteins and the permeability of this membrane to calcium have been established.