Ultracytochemical localization of Ca++-ATPase activity in pituicytes of the neurohypophysis of the guinea pig |
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Authors: | H J Bambauer S Ueno H Umar Prof Dr M Ueck |
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Institution: | (1) Department of Anatomy and Cytobiology, Justus Liebig University, Giessen, Federal Republic of Germany;(2) Department of Ophthalmology, Faculty of Medicine, Kyoto University, Kyoto, Japan;(3) Department of Anatomy and Cytobiology, Aulweg 123, 63 Giessen, Federal Republic of Germany |
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Abstract: | Summary Ca++-ATPase activity (cf. Ando et al. 1981) was examined both light- and electron-microscopically in the neurohypophysis of the guinea pig. Apart from a strong activity within the walls of the blood vessels, in the parenchyma of the neurohypophysis the reaction product of the Ca++-ATPase activity was restricted to the plasmalemma of the pituicytes. This reaction was completely dependent upon Ca++ and the substrate, ATP; the reaction was inhibited by 0.1 mM quercetin, an inhibitor of Ca++-ATPase. A reduction of the enzyme activity occurred by 1) adding Mg++ to the standard incubation medium, and 2) substituting Ca++ with Mg++ at varing concentrations. In all experiments the neurosecretory fibers were devoid of Ca++-ATPase activity. The function of the Ca++-ATPase activity in the plasmalemma of the pituicytes is discussed in connection with the regulation of the extracellular Ca++ concentration, which seems to be important with respect to the discharge of secretory material from the neurosecretory fibers.Fellow of the Alexander von Humboldt Foundation, Bonn, Federal Republic of Germany. |
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Keywords: | CA++-ATPase Pituitary gland pars nervosa Pituicytes Neurosecretion Guinea pig |
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