The release of Ca²⁺ from internal stores is a major source of signal Ca²⁺ in almost all cell types. The internal Ca²⁺ pools are activated via two main families of intracellular Ca²⁺-release channels, the ryanodine and the inositol 1,4,5-trisphosphate (InsP₃) receptors. Among multicellular organisms these channel types are ubiquitous, whereas in most unicellular eukaryotes the identification of ...

Calcium release from intracellular stores is a common phenomenon in cells. Calcium release is mediated by two classes of Ca2+ release channels, the ryanodine receptors (RyRs) and the inositol trisphosphate receptors (IP3Rs). There are three types of RyR and three types of IP3Rs. Different cells have different complements of RyR and IP3Rs. In most cases, it is clear what turns-on these channels....

Pig oocytes matured in vitro are parthenogenetically activated after treatment with nitric oxide (NO)-donor SNAP. The chelation of intracellular calcium ions with BAPTA-AM suppressed the SNAP-induced activation in a dose-dependent manner. Activation by a NO-donor is dependent on the influx of calcium from extracellular spaces, because the blockage of calcium channels by verapamil had significan...

Fluorescent ryanodine revealed the distribution of ryanodine receptors in the submembrane cytoplasm (less than a few micrometers) of cultured bullfrog sympathetic ganglion cells. Rises in cytosolic Ca(2+) ([Ca(2+)](i)) elicited by single or repetitive action potentials (APs) propagated at a high speed (150 microm/s) in constant amplitude and rate of rise in the cytoplasm bearing ryanodine recep...

Cyclic-ADP-ribose (cADPR) has been reported to serve as a second messenger to mobilize intracellular Ca2+ independent of IP3 in a variety of mammalian cells. This cADPR-mediated Ca2+ signaling pathway importantly participates in the regulation of various cell functions. The present study determined the role of endogenous cADPR in mediating ryanodine-sensitive Ca2+-induced Ca2+ release (CICR) in...

We have previously reported that injection of ryanodine receptor agonists into mature bovine oocytes induces intracellular calcium release, indicative of the existence of ryanodine receptors. In this experiment, further evidence of the ryanodine receptor localization, and developmental regulation in bovine oocytes is presented. The possible physiological significance is also suggested. Using a ...

Differentiation and morphogenesis of skeletal muscle are complex and asynchronous events that involve various myogenic cell populations and extracellular signals. Embryonic and fetal skeletal myoblasts are responsible for the formation of primary and secondary fibers, respectively, although the mechanism that diversifies their fate is not fully understood. Calcium transients appear to be a sign...

The skeletal muscle relaxant dantrolene inhibits the release of Ca from the sarcoplasmic reticulum during excitation-contraction coupling and suppresses the uncontrolled Ca release that underlies the skeletal muscle pharmacogenetic disorder malignant hyperthermia; however, the molecular mechanism by which dantrolene selectively affects skeletal muscle Ca regulation remains to be defined. Here w...

Bai Y, Edelmann M, Sanderson MJ. The contribution of inositol 1,4,5-trisphosphate and ryanodine receptors to agonist-induced Ca signaling of airway smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 297: L347–L361, 2009. First published May 22, 2009; doi:10.1152/ajplung.90559.2008.—The relative contribution of inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) and ryanodine receptors (Ry...