Effect of doxorubicin on calcium binding sites in guinea-pig heart

Cardiotoxicity induced by doxorubicin in vivo: protective activity of the spin trap alpha-phenyl-tert-butyl nitrone

The role of free radical generation in the development of the acute cardiotoxicity induced by doxorubicin (DXR) in the rat and the protective activity of anti-radical drugs were investigated in in vivo experiments by evaluating the body weight curve, ECG, contractile performance and coronary flow up to 10 days after DXR. A lipophilic spin trap (alpha-phenyl-tert-butyl nitrone, PBN) was continuously administered at a dose of 0.65 mg/kg every hour for 2 weeks by an intraperitoneal osmotic pump. DXR was administered i.v. at a dose of 9 mg/kg 3 days after beginning the PBN infusion. DXR impaired ECG and body weight gain after 3 days (partly reversible at later times), while contractility and coronary flow were significantly impaired throughout the experimental time. PBN was shown to prevent the DXR-induced alterations of contractility and coronary flow, while ECG was non-significantly improved. The body weight curve was not affected. Since the dose of PBN used does not produce pharmacological effects, the protective activity in rats receiving DXR indicates that free radicals may play a causal role in the acute cardiotoxicity in vivo. The use of suitable spin traps and administration schedules seems to be an interesting approach for the prevention of radical-dependent pathologies.

Cardiotoxicity and antitumor activity of a copper(II)-doxorubicin chelate

The cardiotoxic and cytotoxic effects of the Cu(II)-doxorubicin (DXR) complex [Cu(DXR)]n are compared with those of the parent drug. It is shown that 10(-4) M [Cu(DXR)]n has no depressant effects on isolated rat atria, in contrast with an equimolar concentration of the parent drug. No differences were found between the cytotoxic activities of the Cu(II) complex and free DXR on B16 melanoma and HeLa cells. A reduced penetration of the polymeric [Cu(DXR)]n into the myocardial cells as compared with the free drug was invoked to account for the absence of cardiotoxicity of the DXR complex. On the other hand, the observation that copper-complexation does not affect the cytotoxicity of the drug suggests that extracellular as well as intracellular mechanisms may be involved in the development of its antitumor activity.

Evaluation of membrane fluidity effects and enzyme activities alterations in adriamycin neurotoxicity

Adriamycin (ADR) increased the lipid fluidity of dog brain synaptosomal plasma membranes (SPM) labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH), as indicated by the steady-state fluorescence anisotropy [(ro/r)-1]-1. Arrhenius-type plots of [(ro/r)-1]-1 indicated that the lipid phase separation of the membrane at 23.3 +/- 1.2 degrees was perturbed by ADR such that the temperature was reduced to 16.2 +/- 1.1 degrees. Arrhenius plots of (Na+ + K+)-stimulated ATPase activity exhibited a break point at 22.8 +/- 1.1 degrees in control SPM which was reduced to 15.8 +/- 1.0 degrees in ADR treated SPM, suggesting differences in the interaction of (Na+ + K+)-stimulated ATPase with lipids between ADR treated and untreated SPM. (Na+ + K+)-stimulated ATPase and Ca2+-stimulated ATPase activities were increased at a concentration range 10(-18)-10(-15) M of ADR; higher concentrations (up to 10(-7) M), however, led to a progressive inhibition of the enzyme activities. The allosteric properties of SPM-bound (Na+ + K+)-stimulated ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by ADR whereas those of SPM-bound acetylcholinesterase remained unaffected. We propose that ADR achieves these effects through asymmetric perturbations of the membrane lipid structure and that changes in membrane fluidity may be an early key event in ADR induced neurotoxicity.