ISSN:
1432-1912
Schlagwort(e):
Ca-Inward Current
;
EC Coupling
;
Cardiac Excitability
;
Verapamil
;
D 600-KCl Depolarization
;
g Ca
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Summary Cat papillary muscles were depolarized by raising the external K concentration so that resting potential went from about −80 mV to −50 mV. This caused inactivation of the transmembrane Na system. The remaining Ca-mediated action potentials showed greater overshoot, reduced upstroke velocity and action potential duration, and higher threshold of excitation. A graded electrical response to stimulous strength was also present. These action potentials depended mainly on the extracellular Ca concentration [16]. Further, the specific Ca-antagonistic compounds verapamil and D 600 [10] or Ca-with-drawal completely abolished the ability of the K-depolarized fibres to respond to stimulation with propagated electrical activity. Conversely, extra Ca, epinephrine or isoproterenol overcame this inhibitory effect by increasing the Ca transmembrane influx. Also, within 1 min after returning treated muscles to normal K 0 Tyrode solution, the Na system was reactivated and apparently normal electrical activity possible. In this case, Ca-withdrawal and the Ca-antagonists lose their electrical inhibitory influence, while excitation-contraction uncoupling still persist.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00501349
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