RESUMEN
The use of doxorubicin, a clinically important antitumor agent, is associated with toxic cardiac side effects, including arrhythmias and, on rare occasions, sudden death. We have used aggregates of cultured chick embryonic heart cells, a preparation free of neuronal and vascular elements, to investigate the direct effects of doxorubicin on automaticity. Under control conditions, normally quiescent aggregates of ventricular origin could be induced to contract spontaneously during a 24- to 48-h incubation with doxorubicin. The percentage of aggregates exhibiting automaticity was concentration dependent between 0.01 and 1 microM doxorubicin. At relatively high drug exposure (e.g., 1 microM doxorubicin for 48 h), beating was shown to be dysrhythmic. Whereas control aggregates exhibited large stable resting potentials on impalement with intracellular microelectrodes, treated aggregates exhibited spontaneous action potentials with Phase 4 depolarization. Doxorubicin, in a dose-dependent manner, increased the rate of Phase 4 depolarization, reduced the maximum diastolic potential, and shortened the action potential duration. In dysrhythmic aggregates, microelectrode recordings also revealed examples of premature depolarizations, extrasystoles, and dropped beats. This study provides the first cellular electrophysiological recordings of doxorubicin-induced automaticity and rhythm disturbances in heart muscle. The results suggest that the induction of automaticity is due to a depolarizing action of doxorubicin on the cardiac membrane.
Asunto(s)
Doxorrubicina/farmacología , Corazón/fisiología , Miocardio/citología , Potenciales de Acción/efectos de los fármacos , Animales , Agregación Celular/efectos de los fármacos , Células Cultivadas , Embrión de Pollo , Conductividad Eléctrica , Corazón/efectos de los fármacos , MicroelectrodosAsunto(s)
Inhibidores de Adenilato Ciclasa , Agonistas alfa-Adrenérgicos/fisiología , Receptores Adrenérgicos alfa/metabolismo , Animales , Plaquetas/fisiología , Membrana Celular/fisiología , Células Cultivadas , Humanos , Iones/farmacología , Cinética , Ratones , Neuronas/fisiología , Ratas , Receptores Adrenérgicos alfa/efectos de los fármacos , Ribonucleótidos/farmacologíaAsunto(s)
Adenilil Ciclasas/metabolismo , Receptores Adrenérgicos alfa/metabolismo , Receptores Adrenérgicos/metabolismo , Agonistas alfa-Adrenérgicos/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Plaquetas/metabolismo , Membrana Celular/metabolismo , Células Cultivadas , Epinefrina/metabolismo , Guanosina Trifosfato/farmacología , Humanos , Imidazoles/farmacología , Técnicas In Vitro , Magnesio/farmacología , Cloruro de Magnesio , Músculo Liso/metabolismo , Prazosina/metabolismo , Unión ProteicaAsunto(s)
Adenilil Ciclasas/metabolismo , Glioma/metabolismo , Neuroblastoma/metabolismo , Receptores Adrenérgicos alfa/metabolismo , Receptores Adrenérgicos/metabolismo , Agonistas alfa-Adrenérgicos/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Animales , Membrana Celular/metabolismo , Epinefrina/metabolismo , Células Híbridas/metabolismo , Cinética , Neoplasias Experimentales/metabolismo , Ensayo de Unión RadioliganteRESUMEN
Intracranial injections of [32P]orthophosphate readily label a number of brain phosphoproteins as resolved by polyacrylamide gel electrophoresis. The majority of these in vivo labeled phosphoproteins co-migrate with phosphoproteins that are labeled in vitro by incubation of brain membranes with [32P]ATP. Two of the major in vitro labeled phosphoproteins with apparent molecular weights of 47,000 (band F1) and 41,000 (band F2) are rapidly labeled in vivo. Since they are rapidly dephosphorylated in vitro, this suggests a high rate of phosphate turnover. The electrophoretic pattern of in vivo labeled phosphoproteins did not appear to be altered by the method of sacrifice (focused microwave irradiation, decapitation or liquid nitrogen immersion) or by the state of the animal at the time of labeling (awake or lightly anesthetized with pentobarbital). The reduction of phosphatase activity during tissue processing at 0 degree C may account for the similarities observed with different sacrifice methods. Removal of phospholipids or polynucleotides had little effect on the in vivo labeled 32P-containing bands. However, alkaline hydrolysis or protease treatment uniformly reduced the radioactivity in the labeled bands. These findings suggest that the 32P-containing bands consist of phosphoester linkages to serine or threonine residues. The present evidence emphasizes that previously characterized in vitro labeled brain phosphoproteins are, in fact, labeled in the awake, freely-moving animal.