title: [Influence of oxidative processes in mitochondria on contractility of the frog Rana temporaria heart muscle. Effects of cadmium].
abstract: The inotropic Cd2+ action on frog heart is studied with taking into account its toxic effects upon mitochondria. Cd2+ at concentrations of 1, 10, and 20 microM is established to decrease dosedependently (21.3, 50.3, and 72.0%, respectively) the muscle contraction amplitude; this is explained by its competitive action on the potential-controlled Ca2(+)-channels of the L-type (Ca 1.2). In parallel experiments on isolated rat heart mitochondria (RHM) it was shown that Cd2+ at concentrations of 15 and 25 microM produces swelling of non-energized and energized mitochondria in isotonic (with KNO2 and NH4NO3) and hypoosmotic (with 25 mM CH3COOK) media. Study of oxidative processes in RHM by polarographic method has shown 20 microM Cd2+ to disturb activity of respiratory mitochondrial chain. The rate of endogenous respiration of isolated mitochondria in the medium with Cd2+ in the presence of malate and succinate was approximately 5 times lower than in control. In experimental preparations, addition into the medium of DNP-uncoupler of oxidation and phosphorylation did not cause an increase of the oxygen consumption rate. Thus, the obtained data indicate that a decrease in the cardiac muscle contractility caused by Cd2+ is due not only to its direct blocking action on Ca2(+)-channels, but also is mediated by toxic effect on rat heart mitochondria, which was manifested as an increase in ion permeability of the inner mitochondrial membrane (IMM), acceleration of the energy-dependent K+ transport into the matrix of mitochondria, and inhibition of their respiratory chain.
authors.forename: I V
authors.initials: IV
authors.lastname: Shemarova
authors.forename: S M
authors.initials: SM
authors.lastname: Korotkov
authors.forename: V P
authors.initials: VP
authors.lastname: Nesterov
mesh_terms: D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D053142:Mitochondrial Size / Q000187:drug effects; D008933:Mitochondrial Swelling / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects*; D010101:Oxygen Consumption; D011896:Rana temporaria; D051381:Rats; D017208:Rats, Wistar; D013053:Spectrophotometry
chemical_list: D002104:Cadmium