title: Is digitalis compound-induced cardiotoxicity, mediated through guinea-pig cardiomyocytes apoptosis?
abstract: Our aim in performing this study was to analyze in vivo the cell death mechanism induced by toxic doses of digitalis compounds on guinea-pig cardiomyocytes. We analyzed three study groups of five male guinea pigs each. Guinea pigs were intoxicated under anesthesia with ouabain or digoxin (at a 50-60% lethal dose); the control group did not receive digitalis. A 5-hours period elapsed before guinea pig hearts were extracted to obtain left ventricle tissue. We carried out isolation of mitochondria and cytosol, cytochrome c and caspase-3 and -9 determination, and electrophoretic analysis of nuclear DNA. TdT-mediated DUTP-X nick end labeling (TUNEL) reaction was performed in histologic preparations to identify in situ apoptotic cell death. Ultrastructural analysis was performed by electron microscopy. Electrophoretic analysis of DNA showed degradation into fragments of 200-400 base pairs in digitalis-treated groups. TUNEL reaction demonstrated the following: in the control group, <10 positive nuclei per field; in the digoxin-treated group, 2-14 positive nuclei per field, while in the ouabain-treated group counts ranged from 9-30 positive nuclei per field. Extracts from ouabain-treated hearts had an elevation of cytochrome c in cytosol and a corresponding decrease in mitochondria; this release of cytochrome c provoked activation of caspase-9 and -3. Electron microscopy revealed presence of autophagic vesicles in cytoplasm of treated hearts. Toxic dosages of digitalis at 50-60% of the lethal dose are capable of inducing cytochrome c release from mitochondria, processing of procaspase-9 and -3, and DNA fragmentation; these observations are mainly indicative of apoptosis, although a mixed mechanism of cell death cannot be ruled out.
authors.affiliation: Departamento de Farmacologia, Instituto Nacional de Cardiologia Ignacio Chavez, Juan Badiano 1, Col. Seccion XVI, 14080 Mexico, D. F., Mexico. margarita0022@yahoo.com
authors.forename: Margarita
authors.initials: M
authors.lastname: Ramirez-Ortega
authors.forename: Gabriela
authors.initials: G
authors.lastname: Zarco
authors.forename: Vilma
authors.initials: V
authors.lastname: Maldonado
authors.forename: Jose F
authors.initials: JF
authors.lastname: Carrillo
authors.forename: Pilar
authors.initials: P
authors.lastname: Ramos
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ceballos
authors.forename: Jorge
authors.initials: J
authors.lastname: Melendez-Zajgla
authors.forename: Noemí
authors.initials: N
authors.lastname: Garcia
authors.forename: Cecilia
authors.initials: C
authors.lastname: Zazueta
authors.forename: Jose
authors.initials: J
authors.lastname: Chanona
authors.forename: Jorge
authors.initials: J
authors.lastname: Suarez
authors.forename: Gustavo
authors.initials: G
authors.lastname: Pastelin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004071:Digitalis Glycosides / Q000633:toxicity*; D006168:Guinea Pigs; D020287:In Situ Nick-End Labeling; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D009206:Myocardium / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D010042:Ouabain / Q000633:toxicity
chemical_list: D002316:Cardiotonic Agents; D002843:Chromatin; D004071:Digitalis Glycosides; D010042:Ouabain; D045304:Cytochromes c; D053148:Caspase 3; D053453:Caspase 9