Ontogenic and phylogenic studies of intestinal, hepatic, and placental alkaline phosphatases. Evidence that intestinal alkaline phosphatase is a late evolutionary development.

We have studied the intrauterine development of guinea pig and rat organ phosphatases using biochemical, immunologic, and histologic techniques. In all organs tested the features of the adult phosphatase activity were achieved during the second or third gestational phases. In the rat, the tissue-unspecific phosphatase activity was found by immunoprecipitation with antiserum to rat liver phosphatase in all gestational phases in liver and placenta. The high liver activity in the first phase of gestation corresponded to hematopoietic cells. Hepatocyte phosphatase did not appear until the second gestational phase. The tissue-unspecific phosphatase activity was found in the first and second gestational phase in surface intestinal epithelial cells, even after crypt formation occurred. Once phosphatase appeared in enterocytes on villi, only the intestinal-type enzyme was detected. Alkaline phosphatase was measured in the liver and intestine from animals in various phyla. In fish and reptiles, the intestinal activity had the enzymatic characteristics of the tissue-unspecific enzyme. The appearance of intestinal alkaline phosphatase with unique properties and high specific activity is a characteristic of mammals.