Mechanisms underlying post-rest potentiation in isolated left rat atria.
In the isolated rat left atria the influence of rest intervals on the force developed by the first post rest beat (PRB) was studied. Under control conditions the force developed by the PRB increased (respect to previous steady state at 0.5 Hz) with the increase of the rest interval until 20 sec of pause and decreased with longer intervals. In the presence of caffeine (1 or 4 mM plus high [Ca]0) there was a monotonous fall of the PRB as a function of the rest interval. When extracellular calcium was replaced by Sr the tension developed by PRB vs. rest interval curve rose with a slope lower than the control one and reached the peak at 60 sec. At saturation levels of [Ca]0 the PRB tension development did not vary up to 20 sec pause but the decreasing phase observed after 20 sec of rest interval was still present. At 0.5 mM [Ca]0 the response was similar to control curve. The results in the presence of caffeine and strontium suggest that, in rat atria, the rest potentiation appears to be dependent on the release of calcium from intracellular stores (sarcoplasmic reticulum). This is consistent with the hypothesis proposing that longer resting periods provide a longer interval for the transfer of Ca from uptake to release sites in the sarcoplasmic reticulum.
Marengo
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F
Instituto de Investigaciones Cardiológicas, Facultad de Medicina, U.B.A., Argentina.
Márquez
M T
MT
Aramendia
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P
D000704:Analysis of Variance; D000818:Animals; D016275:Atrial Function; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D005260:Female; D008564:Membrane Potentials / Q000187:drug effects; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013324:Strontium / Q000494:pharmacology*
D002110:Caffeine; D002118:Calcium; D013324:Strontium