Angiotensin II regulation of intracellular calcium in astroglia cultured from rat hypothalamus and brainstem.
This study examines the angiotensin II (Ang II) regulation of intracellular free calcium concentration ([Ca2+]i) in astroglia cultured from the hypothalamus and brainstem of the adult rat. Bath perfusion or rapid puffer application of angiotensin II (Ang II) (1-100 nM) increased [Ca2+]i in both polygonal and stellate astroglia when measured using fura-2 imaging fluorescence microscopy. Ang II increased [Ca2+]i in 96.1 and 95.6% of the polygonal and stellate glial cells, respectively. In normal Tyrode's solution (containing 2 mM CaCl2), the Ang II-stimulated increase in [Ca2+]i characteristically showed a biphasic response, i.e., an initial rapid transient peak followed by a sustained, steady-state plateau of free Ca2+. In both cell types, the selective Ang II type 1 receptor subtype (AT1) antagonist losartan (1 microM) inhibited the Ang II-stimulated increase in [Ca2+]i. The selective AT2 antagonist PD 123319 (1 microM) did not inhibit the Ang II-stimulated increase in [Ca2+]i in either cell type. To define the sources of Ca2+ that participate in the Ang II-stimulated increase in [Ca2+]i in astroglia, experiments were performed in a nominally Ca(2+)-free Tyrode's solution. In either cell type, this resulted in only an initial transient increase of Ca2+ and no sustained plateau of Ca2+ when challenged with Ang II. Thapsigargin (5 microM), cyclopiazonic acid (10 microM), and ryanodine (10 microM), but not caffeine (1-10 mM), inhibited the initial rise in [Ca2+]i. The plateau increase of [Ca2+]i caused by Ang II (100 nM) was reversibly inhibited by both cadmium (100 microM) and nifedipine (10 microM); in contrast, gadolinium (100 microM) had no effect on the plateau increase of [Ca2+]i. These results indicate that Ang II, in physiological concentrations, can activate AT1 receptors to stimulate both Ca2+ release from intracellular stores and Ca2+ influx from the extracellular space to increase [Ca2+]i of polygonal and stellate astroglia.
Journal of neurochemistry
Wang, Desuo; Martens, Jeffrey R.; Posner, Philip; Sumners, Colin; and Gelband, Craig H., "Angiotensin II regulation of intracellular calcium in astroglia cultured from rat hypothalamus and brainstem." (1996). PCOM Scholarly Papers. 1149.
This article was published in Journal of Neurochemistry, Volume 67, Issue 3, September 1996.
The published version is available at http://dx.doi.org/10.1046/j.1471-4159.1996.67030996.x
Copyright © 1996 International Society for Neurochemistry