PHYSICOCHEMICAL CHARACTERISTICS OF THE TERBIUM-ADRIAMYCIN COMPLEX AND ITS EFFECTS ON THE SINUS NODE AUTOMATICITY

被引:10
作者
CANADA, RG
CARPENTIER, RG
机构
[1] Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC
关键词
TERBIUM-ADRIAMYCIN COMPLEX; SINUS NODE AUTOMATICITY;
D O I
10.1016/0304-4165(91)90193-K
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The physicochemical characteristics of the terbium-adriamycin complex (terbomycin) were studied. Perturbations in the visible absorption spectrum of adriamycin by terbium (Tb3+) was indicative of formation of the terbomycin complex. The absorption maximum of free adriamycin at 479 nm shifted towards the absorption maximum of terbomycin at 539 nm. The binding of Tb3+ of adriamycin was negligible at acidic pH. At alkaline pH, the affinity of Tb3+ for adriamycin increased. The stoichiometry of binding was estimated to be 0.5: one Tb3+ ion per two adriamycin molecules. Thermodynamic analysis revealed that the spontaneous formation of terbomycin was due to an increase in the entropy of the system. The effects of adriamycin, Tb3+ and terbomycin on sinus node automaticity were studied using sinus node from rats, superfused with modified mammalian Tris-Tyrode's solution (37-degrees-C). The sinus node rate was monitored with intracellular microelectrodes. 25-mu-M Tb3+ increased the sinus node rate. Adriamycin (50-mu-M) depressed sinus node automaticity. Terbomycin also reduced the sinus node rate. There was no difference between the effects of adriamycin and terbomycin. The chronotropic effect of terbomycin persisted in the presence of atropine.
引用
收藏
页码:136 / 141
页数:6
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