ISSN:
1432-1912
Keywords:
k-Strophanthin
;
Digitoxigenin
;
45Calcium
;
Contractile Force
;
Cellular Calcium Content
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The influence of positive inotropic and of toxic concentrations of k-strophanthin and digitoxigenin on contractile force, calcium content and 45calcium exchange was studied in isolated guinea-pig atria; at the same time the extracellular space of each preparation was determined. 1. In the concentration range used (0.8–13.4 μM) the two agents did not show any effect on the extracellular space. 2. Positive inotropic concentrations of k-strophanthin and digitoxigenin induced a significant decrease in the cellular calcium content as a result of a net increase in calcium efflux. At 3, 5, 10 or 15 min after the addition of the drug the relative specific 45calcium activity (RSA) was increased and was significantly greater than values obtained in control experiments. It is concluded that positive inotropic concentrations enlarge the exchangeable calcium fraction of the myocardial cell. 3a. During the initial positive inotropic phase of action of toxic concentrations of k-strophanthin (2.67 and 13.4 μM) and digitoxigenin (2.67 μM) there was also a significant decrease of the cellular calcium content, which occured more rapidly than that produced by positive inotropic concentrations. 3b. After the occurrence of toxic signs the calcium content of the myocardial cell was significantly increased while the unexchanged calcium fraction remained unchanged in absolute size. The RSA was always significantly increased compared with results from control experiments. It is concluded that the action of toxic concentrations of k-strophanthin and digitoxigenin on the calcium metabolism is due to a marked reduction in calcium efflux. 4. Digitoxigenin increased the contractile force considerably more than k-strophanthin, but had less effect on calcium metabolism. The difference might be due to the different lipophilic properties of the two agents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00501125
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