title: Signal transduction in red blood cells of the lizards Ameiva ameiva and Tupinambis merianae (Squamata, Teiidae).
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 20 nM 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+]c in the cells from both lizard species, mostly by mobilization of the cation from internal stores.
authors.affiliation: Departamento de Fisiologia, Universidade de São Paulo, Instituto de Biociências, São Paulo, Brazil.
authors.forename: F H
authors.initials: FH
authors.lastname: Beraldo
authors.forename: R
authors.initials: R
authors.lastname: Sartorello
authors.forename: R D
authors.initials: RD
authors.lastname: Lanari
authors.forename: C R
authors.initials: CR
authors.lastname: Garcia
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000814:Aniline Compounds / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000032:analysis; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D008116:Lizards / Q000378:metabolism; D008985:Monensin / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D017494:Proton Pumps / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015398:Signal Transduction / Q000502:physiology; D019284:Thapsigargin / Q000378:metabolism / Q000494:pharmacology; D014966:Xanthenes / Q000032:analysis
chemical_list: D000814:Aniline Compounds; D005456:Fluorescent Dyes; D017494:Proton Pumps; D014966:Xanthenes; C059715:Fluo-3; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D008985:Monensin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D009550:Nigericin; D002118:Calcium