[Protection against myocardial ischemia by nisoldipine--an experimental study with valinomycin K-sensitive microelectrodes].
It has been shown that dihydropyridines exert a cardioprotective effect during experimental ischemia. This effect is reflected in a reduced K-efflux from the ischemic tissue. Recently we have shown that ischemic K-efflux is largely mediated by ATP-dependent K-channels. Using K-selective microelectrodes we studied the effect of nisoldipine on K-efflux during simulated ischemia (guinea pig papillary muscle immersed in paraffin oil; normal Tyrode solution, HEPES buffered, 100% O2-equilibrated, 37 degrees C). While ischemic K-efflux was Ca-dependent in stimulated preparations, it was independent of extracellular Ca in resting preparations. Our results show that nisoldipine leads to an inhibition of ischemic K-efflux during simulated ischemia. In resting preparations this inhibition is not a direct Ca-antagonistic effect, since withdrawal of extracellular Ca does not inhibit ischemic K-efflux but nisoldipine does. We suggest a direct effect of nisoldipine on the KATP channel which is mainly responsible for ischemic K-loss.
Köppel
H
H
Klinischen Abteilung für Angiologie, Medizinischen Universitätsklinik Graz.
Gasser
R
R
Pokan
R
R
Willomitzer
R
R
Cichocki
L
L
Pilger
E
E
Klein
W
W
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D046508:Culture Techniques; D004562:Electrocardiography / Q000295:instrumentation*; D006168:Guinea Pigs; D008839:Microelectrodes; D017202:Myocardial Ischemia / Q000503:physiopathology / Q000517:prevention & control*; D015737:Nisoldipine / Q000494:pharmacology*; D010210:Papillary Muscles / Q000187:drug effects / Q000503:physiopathology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D014634:Valinomycin
D002121:Calcium Channel Blockers; D015221:Potassium Channels; D014634:Valinomycin; D015737:Nisoldipine; D011188:Potassium
Myokardiale Ischämieprotektion durch Nisoldipin--eine experimentelle Untersuchung mit Valinomycin-K-sensitiven Mikroelektroden.