Alkaline phosphatase, 5?-nucleotidase and ATPase activity in the molar region of the mouse

Abstract

The distribution of nonspecific alkaline phosphatase (EC 3.1.3.1), ATPase (EC 3.6.1.3) and 5′-nucleotidase (EC 3.1.3.5) was studied by histochemical calcium and lead methods in the molar region of newborn mice. Glycerophosphate (GP), adenosine triphosphate (ATP) and adenosine monophosphate (AMP) were tested as enzyme substrates. In order to distinguish between hydrolysis catalyzed by nonspecific alkaline phosphatase and hydrolysis mediated by more substrate specific phosphatases, inhibitors of different phosphatase activities were added to the incubation media. Alkaline phosphatase (EC 3.1.3.1), assayed as GPase in osteoblasts, cells of the stratum intermedium, odontoblasts, cells of the subodontoblastic layer and blood vessel walls was completely inhibited by R 8231, BAL and EDTA and almost completely inhibited by L-cysteine and levamisole. The AMP-hydrolyzing capacity in the cells mentioned above was identically affected and was considered to be due to nonspecific alkaline phosphatase. In the oral epithelium and the external dental epithelium, on the other hand, the AMPase activity recorded with the lead method (pH 7.2) was not affected by these inhibitors while Zn2+ ions caused inhibition. In view of these findings the AMP-hydrolysis in oral epithelium and external dental epithelium was considered to be due to 5′-nucleotidase (EC 3.1.3.5). The ATPase activity in ameloblasts, tongue muscle fibres and blood vessel walls was unaffected by R 8231 and levamisole and enhanced by BAL and L-cysteine. Treatment with EDTA increased the ATPase activity recorded in muscle fibres and blood vessel walls. The major part of the ATP-hydrolyzing capacity in osteoblasts, cells of the stratum intermedium and odontoblasts was inhibited by R 8231 BAL and EDTA. The hydrolysis of ATP recorded after inhibition by R 8231, BAL or EDTA is likely to be due to activity of substrate-specific ATPase(s) (EC 3.6.1.3).