Basal Spontaneous Firing of Rabbit Sinoatrial Node Cells Is Regulated by Dual Activation of PDEs (Phosphodiesterases) 3 and 4

Tatiana M. Vinogradova, Syevda Sirenko, Yevgeniya O. Lukyanenko, Dongmei Yang, Kirill V. Tarasov, Alexey E. Lyashkov, Nevin J. Varghese, Yue Li, Khalid Chakir, Bruce Ziman, Edward G. Lakatta

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Background: Spontaneous firing of sinoatrial node cells (SANCs) is regulated by cAMP-mediated, PKA (protein kinase A)-dependent (cAMP/PKA) local subsarcolemmal Ca2+ releases (LCRs) from RyRs (ryanodine receptors). LCRs occur during diastolic depolarization and activate an inward Na+/Ca2+ exchange current that accelerates diastolic depolarization rate prompting the next action potential. PDEs (phosphodiesterases) regulate cAMP-mediated signaling; PDE3/PDE4 represent major PDE activities in SANC, but how they modulate LCRs and basal spontaneous SANC firing remains unknown. Methods: Real-time polymerase chain reaction, Western blot, immunostaining, cellular perforated patch clamping, and confocal microscopy were used to elucidate mechanisms of PDE-dependent regulation of cardiac pacemaking. Results: PDE3A, PDE4B, and PDE4D were the major PDE subtypes expressed in rabbit SANC, and PDE3A was colocalized with μ-actinin, PDE4D, SERCA (sarcoplasmic reticulum Ca2+ ATP-ase), and PLB (phospholamban) in Z-lines. Inhibition of PDE3 (cilostamide) or PDE4 (rolipram) alone increased spontaneous SANC firing by ≈20% (P<0.05) and ≈5% (P>0.05), respectively, but concurrent PDE3+PDE4 inhibition increased spontaneous firing by ≈45% (P<0.01), indicating synergistic effect. Inhibition of PDE3 or PDE4 alone increased L-type Ca2+ current (ICa,L) by ≈60% (P<0.01) or ≈5% (P>0.05), respectively, and PLB phosphorylation by ≈20% (P>0.05) each, but dual PDE3+PDE4 inhibition increased ICa,L by ≈100% (P<0.01) and PLB phosphorylation by ≈110% (P<0.05). Dual PDE3+PDE4 inhibition increased the LCR number and size (P<0.01) and reduced the SR (sarcoplasmic reticulum) Ca2+ refilling time (P<0.01) and the LCR period (time from action potential-induced Ca2+ transient to subsequent LCR; P<0.01), leading to decrease in spontaneous SANC cycle length (P<0.01). When RyRs were disabled by ryanodine and LCRs ceased, dual PDE3+PDE4 inhibition failed to increase spontaneous SANC firing. Conclusions: Basal cardiac pacemaker function is regulated by concurrent PDE3+PDE4 activation which operates in a synergistic manner via decrease in cAMP/PKA phosphorylation, suppression of LCR parameters, and prolongation of the LCR period and spontaneous SANC cycle length.

Original languageEnglish (US)
Article numbere005896
JournalCirculation: Arrhythmia and Electrophysiology
Issue number6
StatePublished - Jun 1 2018


  • calcium
  • calcium channel
  • phosphodiesterase
  • phospholamban
  • sarcoplasmic reticulum
  • sinoatrial node

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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