RESUMEN
【Objective】 To explore the roles of 1,4,5-trisphosphate receptor (IP3Rs) and ryanodine receptors (RyRs), the two main Ca2+ release channels in sarcoplasmic reticulum (SR), in the regulation of intracellular Ca2+ oscillations in neonatal rat cardiomyocytes (NRCMs). 【Methods】 We isolated and cultured NRCMs for different days, then loaded them with Ca2+ indicator fura-2 and performed real-time fluorescent imaging. To distinguish the effects of IP3Rs and RyRs, NRCMs were pre-treated with phenylephrine (PE, IP3Rs agonist), caffeine (RyRs agonist), 2-APB (IP3Rs antagonist), and tetracaine (RyRs antagonists), respectively. 【Results】 The cultured monolayer NRCMs showed spontaneous synchronized Ca2+ oscillations. PE activation or 2-APB blockade of IP3Rs increased or reduced the frequency of Ca2+ oscillations in NRCMs, accordingly, with no significant effect on the amplitude of Ca2+ oscillations. Activation of RyRs with caffeine increased the frequency of Ca2+ oscillations, but unsynchronized the intercellular rhythm of calcium release and beating pace, while blocking RyRs with tetracaine completely abolished the Ca2+ oscillations and beats in NRCMs. In addition, the effect of PE stimulation on Ca2+ oscillation frequency gradually decreased along with cultured days. 【Conclusion】 IP3Rs regulate the rhythm of calcium oscillations, whereas RyRs are the main channel for bulky store Ca2+ release.