Role of Inositol-1,4,5-Trisphosphate Receptor in the Regulation of Calcium Transients in Neonatal Rat Ventricular Myocytes

Abstract

Abstract. This study determined the regulatory effect of inositol 1,4,5-trisphosphate receptors (IP 3 Rs) on the basal Ca 2+ transients in cardiomyocytes. In cultured neonatal rat ventricular myocytes (NRVMs) at different densities, we used confocal microscopy to assess the effect of IP 3 Rs on the endogenous spontaneous Ca 2+ oscillations through specific activation of IP 3 Rs with myo-IP 3 hexakis (butyryloxymethyl) ester (IP 3 BM), a membrane permeable IP 3 , and interference of IP 3 R expression with shRNA. We found that NRVMs at the monolayer state displayed coordinated Ca 2+ transients with less rate, shorter duration, and higher amplitude compared to single NRVMs. In addition, monolayer NRVMs exhibited 4 or 10 times more increased Ca 2+ transients in response to phenylephrine, an a-adrenergic receptor agonist, or IP 3 BM than single NRVMs did, while the transient pattern remained unaltered, suggesting that the sensitivity of intracellular Ca 2+ response to IP 3 R activation is different between single and monolayer NRVMs. However, interference of IP 3 R expression with shRNA reduced the frequency and amplitude of the spontaneous Ca 2+ fluctuates similarly in both densities of NRVMs, resembling the effects of ryanodine receptor inhibition by ryanodine or tetracaine. Our findings suggest that IP 3 Rs are involved, in part, in the regulation of native Ca 2+ transients, in profiles of their initiation and Ca 2+ release extent, in developing cardiomyocytes. In addition, caution should be paid in evaluating the behavior of Ca 2+ signaling in primary cultured cardiomyocytes at different densities.

Alleviation of palmitic acid‐induced endoplasmic reticulum stress by augmenter of liver regeneration through IP3R‐controlled Ca2+ release

“…The cells were loaded with 2 μM fura-3-AM (excitation λ, 488 nm; emission λ, 515 nm) or fura-2-AM (excitation λ, 405 nm; emission λ, 510 nm). The raw fluorescence intensity (F) data were recorded with a Leica SP8 confocal microscopy (Leica, Wetzlar, Germany), and the cytosolic Ca 2+ levels were normalized by calculating the background-subtracted fluorescence (F/F0), where F0 was the baseline fluorescence intensity obtained in the resting state, and F was the fluorescence intensity measured after HIS stimulation (Wang et al, 2016;Zeng et al, 2014). The curves were recorded by using FACScan flow cytometry (ACEA Bioscience, San Diego, CA) and presented after background subtraction.…”

Norepinephrine-Induced Adrenergic Activation Strikingly Increased the Atrial Fibrillation Duration through β1- and α1-Adrenergic Receptor-Mediated Signaling in Mice

“…Recent reports have documented an important role of α1-AR-mediated signaling including Gq, phospholipase C, inositol triphosphate receptor (IP3R), protein kinase C, and CaMKII in the regulation of Ca 2+ transient in cardiomyocytes [ 38 – 40 ]. In addition, endothelin, which also elicits IP3R, Ca 2+ , and CaMKII-mediated signaling, has been reported to induce elevation of intracellular Ca 2+ concentration through SR Ca 2+ release from IP3R, leading to spontaneous Ca 2+ release from RYR in atrial myocytes [ 41 ].…”