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Angiotensin II Regulation of Intracellular Calcium in Astroglia Cultured from Rat Hypothalamus and Brainstem
Author(s) -
Wang Desuo,
Martens Jeffrey R.,
Posner Philip,
Sumners Colin,
Gelband Craig H.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67030996.x
Subject(s) - angiotensin ii , endocrinology , medicine , thapsigargin , cyclopiazonic acid , losartan , chemistry , angiotensin ii receptor type 1 , calcium , antagonist , intracellular , fura 2 , hepatic stellate cell , hypothalamus , biology , receptor , cytosol , biochemistry , enzyme , blood pressure
This study examines the angiotensin II (Ang II) regulation of intracellular free calcium concentration ([Ca 2+ ] 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 n M ) increased [Ca 2+ ] i in both polygonal and stellate astroglia when measured using fura‐2 imaging fluorescence microscopy. Ang II increased [Ca 2+ ] i in 96.1 and 95.6% of the polygonal and stellate glial cells, respectively. In normal Tyrode's solution (containing 2 m M CaCl 2 ), the Ang II‐stimulated increase in [Ca 2+ ] i characteristically showed a biphasic response, i.e., an initial rapid transient peak followed by a sustained, steady‐state plateau of free Ca 2+ . In both cell types, the selective Ang II type 1 receptor subtype (AT 1 ) antagonist losartan (1 µ M ) inhibited the Ang II‐stimulated increase in [Ca 2+ ] i . The selective AT 2 antagonist PD 123319 (1 µ M ) did not inhibit the Ang II‐stimulated increase in [Ca 2+ ] i in either cell type. To define the sources of Ca 2+ that participate in the Ang II‐stimulated increase in [Ca 2+ ] 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 Ca 2+ and no sustained plateau of Ca 2+ when challenged with Ang II. Thapsigargin (5 µ M ), cyclopiazonic acid (10 µ M ), and ryanodine (10 µ M ), but not caffeine (1–10 m M ), inhibited the initial rise in [Ca 2+ ] i . The plateau increase of [Ca 2+ ] i caused by Ang II (100 n M ) was reversibly inhibited by both cadmium (100 µ M ) and nifedipine (10 µ M ); in contrast, gadolinium (100 µ M ) had no effect on the plateau increase of [Ca 2+ ] i . These results indicate that Ang II, in physiological concentrations, can activate AT 1 receptors to stimulate both Ca 2+ release from intracellular stores and Ca 2+ influx from the extracellular space to increase [Ca 2+ ] i of polygonal and stellate astroglia.