Drugs online research references
Zhonghua Xin Xue Guan Bing Za Zhi. 1989 Apr;17(2):73-6, 125.
[The electrophysiologic effect of atenolol and nitrendipine on normal and ischemic rabbit myocardium in situ. I. Effects on transmembrane potential]
[Article in Chinese]
Ren XL, Lin CX.
Transmembrane potential recording technique was achieved by using microelectrode with multiple impalement. The results showed that atenolol, both in normal and ischemic ventricular cells, produced significant lengthening of APD, but no apparent effects on APA, RS, OS and dv/dt max. Nitrendipine exerted no significant influences on all the parameters in normal and ischemic cells. Thus, it is suggested that beta-receptor blocker, atenolol possessed the characteristics of class III antiarrhythmic drug action on normal and ischemic rabbit heart in situ. This in situ action may provide some explanations for the mechanisms through which beta-blockers afford their beneficial effects of reducing the incidence of sudden death in postmyocardial infarction patients. Another interesting finding was that different parts of the repolarization phase of action potentials responded differently to interfering factors. According to the results obtained by analysing various parts of repolarization, we proposed three new parameters, APD0-50 (action potential duration from 0 to 50% of repolarization), APD50-100 (action potential duration from 50 to 100% of repolarization) and RI (repolarization index), to describe the different changes in various parts of repolarization. Discussion of the significance of these three is presented.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2791879&dopt=Abstract
Zhonghua Xin Xue Guan Bing Za Zhi. 1989 Apr;17(2):77-9, 125.
[The electrophysiologic effect of atenolol and nitrendipine on normal and ischemic rabbit myocardium in situ. II. Effects on effective refractory periods and its dispersion]
[Article in Chinese]
Ren XL, Lin CX.
The study was carried out to determine the effective refractory period (ERP) in central part of ischemic region (CR), boundary of ischemic region (BR) and nonischemic region (NR), after occlusion of left ventricular branch of coronary artery in rabbit heart. The results turned out to be that atenolol produced significant prolongation of ERPs in all three regions before and after ligation of the coronary branch. Atenolol also caused significant reduction in dispersion of ERPs in ischemic heart. Nitrendipine, on the other hand, had no significant effects of all the parameters determined. We also found that slight changes in the absolute value of ERPs would result in much more greater changes in dispersion. So it could be inferred that the dispersion in ERPs among different regions of heart is of greater importance to the genesis and interruption of arrhythmias than ERPs themselves. Lastly, our results supported the view that there is a boundary region surrounding the central part of ischemic region, in which cells were moderately damaged and could be saved by proper treatment.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2791880&dopt=Abstract
Zhonghua Xin Xue Guan Bing Za Zhi. 1989 Apr;17(2):80-2, 125-6.
[The electrophysiologic effect of atenolol and nitrendipine on normal and ischemic rabbit myocardium in situ. III. Effects on ventricular fibrillation threshold]
[Article in Chinese]
Ren XL, Lin CX.
This study was designed to assess myocardial vulnerability by measuring ventricular pacing threshold (VPT), multiple extrasystoles threshold (MET), ventricular tachycardia threshold (VTT) and ventricular fibrillation threshold (VFT) by means of the pulse train stimulating method. The results showed that: (1) VFT is a quantitative index of myocardial vulnerability: (2) MET, positively correlated with VFT, might become a substitute for VFT as an index of vulnerability to ventricular fibrillation: (3) atenolol, both in normal and ischemic myocardium, is able to make a significant elevation of VFT, which is considered as an antifibrillation effect: (4) nitrendipine exerted no apparent effects on all the parameters.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2791881&dopt=Abstract
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