The effect of sodium ethylenediaminetetra-acetate (Na2 EDTA) on the histochemical demonstration of some enzyme activities in neonatal mouse molar tissues

Ultrastructural localization of adenosine triphosphatase in the stellate reticulum, stratum intermedium and ameloblasts of the mouse molar

ATPase activity in the developing first mandibular molar of the mouse was demonstrated at the electron microscopic level with the method of Wachstein & Meisel (1957). It was localized along the cell surfaces of the ameloblast and stratum intermedium interface, the stratum intermedium and the stellate reticulum. The ATPase final reaction product was also present at the cell membranes of the proximal region of adjacent ameloblasts and extended to the level of the nuclei. The demonstration of ATPase mainly on the plasma membranes was similar to the observations by other investigators of various non-odontogenic cell types involved in the exchange of materials across plasma membranes.

Electron microscopic localization of 5'-nucleotidase in the stratum intermedium and ameloblasts

5'-nucleotidase was demonstrated at the fine structural level in the stratum intermedium and ameloblasts of the first mandibular molars of CD-1 mice. The enzyme was localized with the Wachstein & Meisel (1957) method along the plasma membranes of the cells of the stratum intermedium and ameloblasts. While 5'- nucleotidase was present throughout the stratum intermedium, only the proximal region of the plasma membranes of ameloblasts was demonstrably active for this enzyme. 5'-Nucleotidase has been implicated in transport of metabolites across cell membranes, and its localization in the present study supports this implication as well as the transport functions of the stratum intermedium and the stratum intermedium--ameloblastic interface.

Adenosine triphosphate catabolism in homogenates of rat secretory enamel organs incubated in histochemical lead media

To investigate how lead, when used as trapping agent, influences the ATP hydrolysis and to study how ATP is catalyzed in histochemical systems, homogenized secretory enamel organs were incubated in histochemical [3H]-ATP media. Aliquots from the media were taken after 3, 10, 20 and 30 min, the ATP and formed metabolites were separated by electrophoresis and radiometrically quantitated. In media lacking both lead and homogenate 2% of the ATP was spontaneously hydrolyzed during 30 min incubation at room temperature. The presence of lead caused an additional 8% hydrolysis at pH 7.2 and an additional 20% hydrolysis at pH 9.4. In the presence of homogenate, however, lead caused a net decrease of the hydrolysis of ATP as well as of ADP and AMP. This enzyme inhibition varied from around zero to some 80%, depending on pH and substrated involved. In homogenate-containing lead media, at both pH 7.2 AND 9.4, ATP was rapidly hydrolyzed primarily to ADP and subsequently to AMP and adenosine and/or inosine. After 5--10 min ADP constituted the predominant substrate at both pH:s. At pH 7.2 ADP remained so for the rest of the incubation, whereas at pH 9.4 AMP was predominant substrate at the end of the incubation. AMP was the finan catabolic product in experiments at pH 7.2, and adenosine and/or inosine at pH 9.4. Inorganic phosphate was liberated almost linearly during the whole incubation period. The results indicate that histochemical studies of substrate specific ATP-ases should be performed with short incubation times and, when high specific activities are present, in large quantities of incubation media to reduce interference by ADP and AMP hydrolyzing enzymes.

Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.

Histochemical demonstration of dehydrogenase activities during late molar crown development and tooth eruption in the mouse

Lactate, malate, and glucose-6-phosphate dehydrogenase activities were demonstrated in the molar tooth and surrounding tissues of the mouse. Intense activities were observed, especially in the reducing dental epithelium. The staining reactions facilitated morphological studies.