Adenosine-induced changes in atrial action potential: Contribution of Ca and K currents

S. Visentin, S. N. Wu, L. Belardinelli

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47 Citations (Scopus)

Abstract

In this study, we examined the relative contribution of the increase in acetylcholine-regulated potassium current (I(K ACh)) and decrease in calcium current (I(Ca)) to the adenosine (Ado)-induced shortening of action potential duration (APD). In isolated guinea pig atrial myocytes, membrane potentials and currents were measured by the whole cell patch-clamp technique. I(Ca) and I(K ACh) were individualized by blocking the K currents with Cs+ and I(Ca) with Cd2+. The effects of Ado on membrane potential and currents were concentration dependent. Ado (10 μM) shortened APD at 0 mV and at 90% of repolarization (APD0, 90) to 7 ± 1 and 26 ± 6 ms from control values of 23 ± 3 and 89 ± 6 ms, respectively. Concomitant with the changes in APD, Ado decreased I(Ca) from -9.2 ± 1.3 to -6.8 ± 10 μA/μF (26% decrease) but increased I(K ACh) from +3.5 ± 0.5 to +7.8 ± 0.8 μA/μF (123% increase). When rundown of I(Ca) was taken into account, the maximum decrease in I(Ca) caused by Ado was 12%. The effect of Ado on I(Ca) and I(K ACh) was not altered by treatment of the cells with either Cs+ or Cd2+. The shortening of APD0, 90 strongly correlated with the increase in I(K ACh) but minimally with the decrease in I(Ca). A 22% reduction in I(Ca) caused by lowering extracellular Ca2+ concentration ([Ca2+](o)) from 3.6 to 1.8 mM was associated with an 11 and 14% shortening of APD0 and APD90, respectively. In the same myocytes an 18% decrease in I(Ca) by 10 μM Ado reduced APD0 and APD90 by 58 and 61%, respectively. In conclusion, the effects of Ado on membrane potential in atrial myocytes are predominantly due to activation of I(K ACh).

Original languageEnglish
Pages (from-to)H1070-H1078
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume258
Issue number4 27-4
DOIs
Publication statusPublished - 1990

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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