The histochemical localization of acid phosphatase activity in BMU

Abstract

In order to clarify the coupling mechanism (or phenomena) of the bone resorption-formation in the remodeling process, this study was attempted to observe the histochemical location of acid phosphatase (ACPase) and tartrate-resistant ACPase (TRACPase) activity of the newly formed cement lines and the mononuclear cells in BMU (basic multicellular unit) using JB-4 embedding technique for the demonstration of ACPase and TRACPase activity on the tibial metaphysis of rat. The ACPase activity could principally be observed both at the sites where the onset of the newly cement line formation of the trabecular bone and the endosteal bone surfaces, and the resorbed bone surfaces. However, the ACPase reactive cement line was never observed at the erosion zone of the tibial metaphysis, where the osteoblastic bone formation does not occur. Other than osteoclasts and cement lines, the ACPase activity was also observed either in the mononuclear cells closely located to the ACPase positive resorbed bone surfaces or the osteocytes near the osteoclasts. They were also positive for the TRACPase reaction. It was concluded that the active osteoclasts are moving on the bone surface as secreting ACPase to form the cement line, which may influence to induce osteoblasts from adjacent preosteoblasts. It was also suggested that the mononuclear cells and the osteocytes may also relate to the bone remodeling.