Histochemical and biochemical study of acid phosphatase in resorbing bone in culture

Abstract

Calvaria removed from 5-day old mice and placed in tissue culture with or without parathyroid extract were studied histochemically and biochemically for their acid phosphatase activity. Calvaria removed directly from the animal or maintained in tissue culture without parathyroid extract exhibited moderate acid phosphatase activity primarily in cells at the endocranial surface of the bone. After 3 days in culture, calvaria treated with parathyroid extract exhibited increased acid phosphatase activity in cells at both the endocranial and epicranial bone surfaces. At the 5th day of culture, parathyroid extract-treated calvaria exhibited intense acid phosphatase activity in the cytoplasm of the numerous osteoclasts associated with areas of resorbing bone. Slight enzymatic activity was also present within osteocytes. Biochemical analyses revealed significantly greater amounts of acid phosphatase in actively resorbing calvaria exposed to parathyroid extract as compared with control calvaria. The peak enzyme activity was found after 5 days in culture and correlated with the period of most rapid resorption. These results further support the concept that there is a relationship between the osteoclast, acid phosphatase, and bone resorption.