Ryanodine in low concentrations is a Ca-release stimulator rather than inhibitor in rat myocardium.
The effects of ryanodine on negative force staircase and potentiated rested-state contraction (RC) in rat myocardium were compared to the action of Ca release stimulator (caffeine) and inhibitors (local anesthetics). Only low ryanodine concentrations (0.1-0.5 mumol/l) were found to reverse anomalous mechanical patterns in rat myocardium to similar to those as generally observed in other mammalian species. Ryanodine-induced positive staircase and a weak RC were potentiated by noradrenaline. The results obtained seem to characterize ryanodine as a Ca2+ release stimulator rather than an inhibitor in this species and suggest different molecular substrates for ryanodine and caffeine inotropy in rat myocardium.
Saxon
M E
ME
Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino, Moscow.
Kobrinski
E M
EM
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012433:Ryanodine / Q000494:pharmacology*; D016276:Ventricular Function
D000470:Alkaloids; D007473:Ion Channels; D012433:Ryanodine; D002110:Caffeine; D002118:Calcium; D009638:Norepinephrine