A comparative histochemical study on alkaline phosphatase of the anterior pituitary gland in various mammals.

Alkaline phosphatase was histochemically studied in the anterior pituitary gland of mammals. By the azo dye method, the enzymatic activity was observed on the cell membrane, and in the cytoplasm and Golgi apparatus of the glandular cells in the swine, dog and guinea pig, while it was found on the cell membrane and in the cytoplasm of the glandular cells in the cattle, sheep and rabbit but only in the cytoplasm of the glandular cells in the hamster, rat and mouse. By the lead citrate method, the enzymatic activity in the glandular cells decreased in all the mammals examined, and was hardly found in the hamster, rat and mouse. It was shown that the localization of alkaline phosphatase activity by the lead citrate method is finer than that by the azo dye method in the anterior pituitary gland. In the swine and dog, the cells with the enzymatic activity were found throughout the gland though they mainly concentrated in the zona tuberalis. In the castrated males, the enzymatic activity was stronger than that in the males and females, and the cells with the activity increased in number. From these results, these cells in the two species studied were regarded as gonadotrophs. Furthermore, it was suggested that the alkaline phosphatase in the glandular cells of the gland displays a high activity in active stage of the synthesis and/or release of gonadotrophic hormone, and have some connection with the regulatory mechanism of membrane permeability.