Divergent calcium signaling in RBCs from <it>Tropidurus torquatus </it>(Squamata – Tropiduridae) strengthen classification in lizard evolution

BMC Physiology. 2007;7(1):7 DOI 10.1186/1472-6793-7-7


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Journal Title: BMC Physiology

ISSN: 1472-6793 (Online)

Publisher: BMC

LCC Subject Category: Science: Physiology

Country of publisher: United Kingdom

Language of fulltext: English

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Garcia Célia RS
Beraldo Flávio H


Blind peer review

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Time From Submission to Publication: 23 weeks


Abstract | Full Text

<p>Abstract</p> <p>Background</p> <p>We have previously reported that a Teiid lizard red blood cells (RBCs) such as <it>Ameiva ameiva </it>and <it>Tupinambis merianae </it>controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na<sup>+</sup>/H<sup>+ </sup>ionophore monensin, K<sup>+</sup>/H<sup>+ </sup>ionophore nigericin and the H<sup>+ </sup>pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca<sup>2+ </sup>from intracellular stores upon ATP addition.</p> <p>Results</p> <p>Here we report, that RBCs from the tropidurid lizard <it>Tropidurus torquatus </it>store Ca<sup>2+ </sup>in endoplasmic reticulum (ER) pool but unlike in the referred Teiidae, these cells do not store calcium in monensin-nigericin sensitive pools. Moreover, mitochondria from <it>T. torquatus </it>RBCs accumulate Ca<sup>2+</sup>. Addition of ATP to a calcium-free medium does not increase the [Ca<sup>2+</sup>]<sub>c </sub>levels, however in a calcium medium we observe an increase in cytosolic calcium. This is an indication that purinergic receptors in these cells are P2X-like.</p> <p>Conclusion</p> <p><it>T. torquatus </it>RBCs present different mechanisms from Teiid lizard red blood cells (RBCs), for controlling its intracellular calcium levels. At <it>T. torquatus </it>the ion is only stored at endoplasmic reticulum and mitochondria. Moreover activation of purinergic receptor, P2X type, was able to induce an influx of calcium from extracelullar medium. These studies contribute to the understanding of the evolution of calcium homeostasis and signaling in nucleated RBCs.</p>