Signal transduction in red bloodcells of the lizards Ameiva ameiva and Tupinambis merianae (Squamata, Teiidae) |
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Authors: | F H Beraldo R Sartorello R D Lanari C R S Garcia |
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Institution: | Universidade de São Paulo, Instituto de Biociências, Departamento de Fisiologia, São Paulo, Brazil |
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Abstract: | The fluorescent calcium probe, Fluo-3, AM was used to measure the intracellular calcium concentration in red blood cells (RBCs) of the teiid lizards Ameiva ameiva and Tupinambis merianae. The cytosolic Ca2+] is maintained around 20nM and the cells contain membrane-bound Ca2+pools. One pool appears to be identifiable with the endoplasmic reticulum (ER) inasmuch as addition of the sarco-endoplasmic reticulum Ca2+ATPase, SERCA, inhibitor thapsigargin induces an increase in cytosolic Ca2+both in the presence and in the absence of extracellular Ca2+. In addition to the ER, an acidic compartment appears to be involved in Ca2+storage, as collapse of intracellular pHgradients by monensin, a Na+–H+exchanger, and nigericin, a K+–H+exchanger, induce the release of Ca2+from internal pools. A vacuolar H+pump, sensitive to NBD-Cl and bafilomycin appears to be necessary to load the acidic Ca2+pools. Finally, the purinergic agonist ATP triggers a rapid and transient increase of Ca2+]cin the cells from both lizard species, mostly by mobilization of the cation from internal stores. |
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