Evidence that zymogen granules do not function as an intracellular Ca2+ store for the generation of the Ca2+ signal in rat parotid acinar cells

The Biochemical Journal
Akihiro NezuYosuke Tojyo

Abstract

Rat parotid acinar cells lacking zymogen granules were obtained by inducing granule discharge with the beta-adrenoceptor agonist isoproterenol. To assess whether zymogen granules are involved in the regulation of Ca(2+) signalling as intracellular Ca(2+) stores, changes in cytosolic free Ca(2+) ion concentration ([Ca(2+)](i)) were studied with imaging microscopy in fura-2-loaded parotid acinar cells lacking zymogen granules. The increase in [Ca(2+)](i) induced by muscarinic receptor stimulation was initiated at the apical pole of the acinar cells, and rapidly spread as a Ca(2+) wave towards the basolateral region. The magnitude of the [Ca(2+)](i) response and the speed of the Ca(2+) wave were essentially similar to those in control acinar cells containing zymogen granules. Western blot analysis of the inositol 1,4,5-trisphosphate receptor (IP(3)R) was performed on zymogen granule membranes and microsomes using anti-IP(3)R antibodies. The immunoreactivity of all three IP(3)Rs was clearly observed in the microsomal preparations. Although a weak band of IP(3)R type-2 was detected in the zymogen granule membranes, this band probably resulted from contamination by the endoplasmic reticulum (ER), because calnexin, a marker protein of...Continue Reading

References

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Citations

Feb 16, 2005·Annual Review of Physiology·James E MelvinTed Begenisich
Sep 16, 2003·American Journal of Respiratory Cell and Molecular Biology·Masami SonHiroaki Kume
Nov 4, 2006·The Journal of Physiological Sciences : JPS·Yutaka EndoMasumi Inoue
Jun 7, 2006·Nihon yakurigaku zasshi. Folia pharmacologica Japonica·Akihiko Tanimura, Yosuke Tojyo

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