LOCALIZATIONS OF ALKALINE AND ACID PHOSPHATASES IN THE EARLY EMBRYOGENESIS OF THE CHICK

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Abstract
The occurrence of acid and alkaline phosphatases in chick embryos from before incubation to 11 days was detd. by the histochemical techniques developed by G. Gomori. The enzymes survive acetone fixation, embedding and mounting on slides; the slides are exposed to Na glycerophosphate soln. containing Pb++ (acid) or Ca++ (alkaline) so that hydrolyzed phosphate is precipitated on the section at the site of enzyme action, and can be visualized by conversion to sulfide. In the chick embryo, both enzymes are present in all undifferentiated tissues from the blastodisc stage, alkaline phosphatase occurring in much higher conc. than acid phosphatase. As differentiation proceeds the phosphatases become less concentrated or disappear in some tissues, become more concentrated in others; in later stages the alkaline enzyme is the more widespread. The changing distributions are descr. in detail, special attention being given to the role of alkaline phosphatase in the formation of long bones. The effects of a var. of chemical agents indicate that the embryonic phosphatases are substantially the same as those descr. in adult tissues; in addition the acid phosphatase was found to be strongly activated by ascorbic acid. Embryonic phosphatases do not seem to be primarily concerned with cell proliferation, but a relation of the enzymes to differentia-tive processes is postulated.