The rapid appearance of acid phosphatase activity at the developing ruffled border of parathyroid hormone activated medullary bone osteoclasts.

The localization of acid phosphatase (ACPase) activity in and near parathyroid hormone (PTH) activated osteoclasts was investigated using electron microscopic cytochemical methods. At 3 hours after oviposition in Japanese Quail hens, medullary bone osteoclasts were highly reactive for ACPase but lacked ruffled borders. There was no evidence of extracellular ACPase activity associated with these osteoclasts. At 20 minutes after PTH administration, osteoclasts had developing ruffled borders and ACPase activity was found in the matrix and extracellular space adjacent to most of these ruffled borders. ACPase activity was seldom observed beyond the resorption zone delineated by the osteoclast clear zones. These results provide direct cytochemical evidence that the ruffled border functions in the release and/or activation of ACPase. In addition, these results show that ACPase localization is rapidly responsive to exogenous PTH.