title: Electron microscopic localization of Mg2+ -dependent adenosine triphosphatase activity in the amphibian pancreas (Salamandra salamandra L. and Rana esculenta L.).
abstract: The ultrastructural distribution of Mg2+ -dependent adenosine triphosphatase (ATPase) activity has been investigated in the salamander and frog pancreas by using glutaraldehyde fixations and a modified Wachstein-Meisel reaction medium. In both species the reaction product (lead phosphate) was found associated with the plasma membrane external side of all islet cell types (B-, A- and D-cells) and of acinar and ductular/centro-acinar cells. Except the apical pole of salamander acinar and centro-acinar cells, usually devoid of reaction, no preferential distribution of enzyme activity depending on endocrine or exocrine cell aspects could be observed. Other specific enzyme localizations included the mitochondria matrices, nucleoles, condensed nuclear chromatin, periaxolemmal spaces in nerve bundles and sometimes the cleft of neuro-glandular junctions. The occurrence of reaction deposits in connective tissue, in the cytoplasm of both islet and exocrine cells and in the nerve fiber axoplasm was considered as a possible diffusion artifact. The reaction intensity, but not its distribution, varied sensibly with the incubation period. 2-iodoacetamide and p-chlormercuribenzoic acid decreased the amount of reaction deposits at the level of all reactive sites and especially in mitochondria. The specificity of Mg2+ -ATPase demonstration in this paper is analysed taking into account several inherent shortcomings of the Wachstein-Meisel incubation medium and of the fixative. The different enzyme localizations, as well as their functional significances are discussed in relation with the findings of other authors.
mesh_terms: D000251:Adenosine Triphosphatases / Q000302:isolation & purification*; D000818:Animals; D001001:Anura; D002462:Cell Membrane / Q000201:enzymology; D002466:Cell Nucleolus / Q000201:enzymology; D008274:Magnesium / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D010179:Pancreas / Q000201:enzymology* / Q000648:ultrastructure; D011893:Rana esculenta / Q000378:metabolism*; D012454:Salamandra / Q000378:metabolism*
chemical_list: D000251:Adenosine Triphosphatases; D008274:Magnesium