A cytochemical study of the calcium-activated adenosinetriphosphatase in hamster adrenal medulla: its occurrence in the Golgi region of chromaffin cells

Tissue fractionation and catecholamines--IV. Adenosine triphosphatase in chromaffin granules: a distribution artefact

Tissue fractionation was used as an analytical tool to study the subcellular distribution of an adenosine triphosphatase activated by Mg2+ in adrenal medullae of the pig and ox and in whole adrenals of the rat. By measuring adenosine triphosphatase and various enzymes in the fractions obtained by differential centrifugation, the distribution pattern of adenosine triphosphatase was found to differ markedly from that of markers like catecholamines, dopamine beta-hydroxylase or cytochrome oxidase. In the pig and ox the distribution of inosine diphosphatase paralleled that of adenosine triphosphatase. After equilibration through sucrose density gradients, no adenosine triphosphatase activity was detected in the chromaffin granules in the rat. However, in bovine adrenal medullae, a large part of the adenosine triphosphatase activity equilibrated in that area of the gradient in which the chromaffin granules were found. This adenosine triphosphatase distribution pattern was an artefact produced by applying a too concentrated sample to the gradient. When a more diluted sample of bovine tissue was used no adenosine triphosphatase activity was found to be associated with the chromaffin granules. The present results lead to a reconsideration of the role of the adenosine triphosphatase in some processes in which the chromaffin granules are involved. Moreover, the degree of purity of many chromaffin granule preparations is again questioned.

Histochemical localization of adenosine triphosphatase activity in thymus: a light microscopical and ultrastructural study

Ultrastructural localization of ATPase at high pH in the presence of Ca2+ showed that activity in thymocyte precursors was stronger than in mature thymocytes. The activity was localized in the nuclear envelope, rough endoplasmic reticulum, Golgi apparatus and mitochondria. The difference in activity was attributed to a marked decrease in ATPase-containing organelles, mainly the endoplasmic reticulum in the mature thymocytes. This appears to be related to the proliferative activity of the cells rather than to the immunological maturity of the thymocytes. A very strong activity, also localized in the same organelles, was present in the macrophages and interdigitating cells which might have a secretory function and possibly contribute to thymocyte maturation. The Ca2+-ATPase activity in the nuclear envelope-endoplasmic reticulum system suggests that these may be the sites for storage and regulation of cytoplasmic calcium.

Ultrastructural localization of adenosine triphosphatase activity in lymphocytes activated in vitro by phytohaemagglutinin

The ultrastructural localization of Ca2+, Mg2+-activated ATPase was studied in phytohaemagglutinin activated lymphocytes and in normal unstimulated lymphocytes. Cells, fixed in paraformaldehyde--glutaraldehyde, were incubated in a medium containing 3 mM ATP, 5 mM CaCl2 and 2.4 mM Pb(NO3)2 in 0.1 M tris buffer at pH 8.5, the optimum pH for histochemical demonstration of this enzyme. Reaction product was localized in the endoplasmic reticulum, nuclear membrane, Golgi apparatus and mitochondria and on the membrane surrounding large electron-dense bodies. Cytoplasmic vesicles and the plasma membrane were negative. Activity in unstimulated lymphocytes showed a similar localization but the amount of endoplasmic reticulum was much less than in activated lymphocytes. The pH of the medium was critical for the localization of the enzyme. At pH 7.5, the cytoplasmic reaction was almost completely inhibited but a dense precipitate was present on the outer surface of the plasma membrane. The reaction was stimulated by either Ca2+ or Mg2+ and was greatly decreased in the absence of these cations or in the presence of p-chloromercuribenzoate or N-ethylmaleimide. Oligomycin inhibited selectively the reaction in mitochondria but not the reaction at other sites. While the reaction in mitochondria showed complete substrate specificity, a mild reaction was obtained at the other sites with uridine diphosphate or sodium beta-glycophosphate as substrate. ATP was, however, the preferential substrate.

Ultrastructural demonstration of Mg-ATPase activity of the chromaffin granule

Histochemical evidence for magnesium-activated-ATPase activity of chromaffin granules in the hamster adrenal medulla is presented. A modified Wachstein-Meisel medium, using 40 mM magnesium, was employed. Not all chromaffin granules were reactive, but the reaction product was more noticable on noradrenaline granules than adrenaline granules. Presumtive exocytotic sites were very reactive. Small vesicles, elongated-granules, lysosomes, the plasma membrane, the endoplasmic reticulum, and mitochondria were also reactive.

Isolation and characterization of myosin from the adrenal medulla

A protein with adenosine triphosphatase activity was isolated from bovine adrenal medulla and subsequently purified by ammonium sulfate precipitation and agarose gel filtration using a discontinuous two-buffer system. Characterization of this protein by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, by assay of the activity of Ca2+, K(+)-EDTA and Mg2+ dependent adenosine triphosphatases by amino acid analysis and by electron microscopy has shown that the adrenal medullary myosin closely resembles those myosins isolated from muscle and other non-muscle cells. The possible roles of myosin in the adrenal medulla are discussed.

Evidence for a plasma membrane calcium pump in bovine adrenal medulla but not adrenal cortex

Continuous sucrose density gradient subfractions from bovine adrenal medullary microsomes were found to accumulate 45-Ca-2+ in the presence of ATP and ammonium oxalate mainly in subfractions of intermediate density. (Na-++K-+)-ATPase (plasma membrane marker) and Ca-2+-ATPase activities were also concentrated in these intermediate subfractions but thiamine pyrophosphatase (Golgi apparatus marker) was not. NADH oxidase (endoplasmic reticulum marker) activity was distributed throughout all subfractions. 45-Ca-2+ accumulation in adrenal cortical microsomes was found to rise and fall in parallel with thiamine pyrophosphatase but not with (Na-++K-+)-ATPase or NADH oxidase activities. Accumulation of 45-Ca-2+ in membrane vesicles in these experiments suggests the existence of a calcium transfer mechanism in plasma membranes of the adrenal medulla but not adrenal cortex.