Changes in autorhythmic heart frequency elicited by redox agents.
In isolated frog heart it was established that methylene-blue (MB, an oxidizing agent) decreased, while ascorbate (ASC, a reducing agent) increased the frequency of autorhythmic heart contractions. After MB treatment, in parallel with this phenomenon, the extracellular K+ concentration [K+]o showed a slow increase, but following ASC application a slow decrease occurred. Since these correlations are in good accordance with the idea that the pacemaking ability of heart, among other properties, depends on the voltage and time-dependent decrease in potassium conductance following the spike, changes in [K+]o might be one mechanism by which oxidizing and reducing agents modulate heart frequencies. On the basis of the effect of insulin (INS) and K-strophantoside (STR) on these modulatory influences, it is presumed that the changes in slow delta [K+]o transients might result, at least partly, from the effect of redox agents on the active transport system. In light of the increase in passive K+ fluxes after oxidant treatment and the decrease in this parameter following reductant treatment an effect of redox agents on the characteristics of the K+-channel is also postulated.
Wittmann
I
I
Central Laboratory of Animal Research, University Medical School, Pécs, Hungary.
Puppi
A
A
Dely
M
M
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D006339:Heart Rate / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000494:pharmacology; D008751:Methylene Blue / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011188:Potassium / Q000378:metabolism; D011893:Rana esculenta; D013328:Strophanthins / Q000494:pharmacology; D013997:Time Factors
D007328:Insulin; D013328:Strophanthins; C008240:K-strophanthoside; D001205:Ascorbic Acid; D011188:Potassium; D008751:Methylene Blue