title: Relationship between the sarcoplasmic reticulum and the plasma membrane.
abstract: Ionic interactions between the plasma membrane (PM) and the sarcoplasmic reticulum (SR) play a crucial role in smooth muscle activation and homeostasis. The most common form of Ca2+ signalling seen in vascular smooth musde of conduit arteries and capacitance veins consists of repetitive asynchronous Ca2+ waves. In the inferior vena cava of the rabbit these waves are initiated by Ca2+ release via InsP3 receptors (InsP3R) and propagated by regenerative Ca2+ release. Maintenance of the [Ca2+] oscillations is dependent on Ca2+ entry through the Na+/Ca2+-exchanger (NCX) which is driven in the reverse mode by Na+ entry through non-specific cation channels. The latter are also responsible for depolarization and activation of voltage-gated Ca2+ channels. The sarcoplasmic-endoplasmic reticulum Ca2+-ATPase (SERCA) in the sheet-like junctional SR is responsible for refilling and completing the cycle. Under resting conditions the interaction between the superficial SR and the NCX is reversed with Ca2+ release channels supplying Ca2+ to the NCX in the PM to be extruded in exchange of extracellular Na+. It is proposed that the above Ca2+ transport between the SR lumen and the extracellular space takes place at PM-SR junctions across a narrow junctional space.
authors.affiliation: The iCAPTUR4E Center, University of British Columbia, St Paul's Hospital, Vancouver, Canada.
authors.forename: Cheng-Han
authors.initials: CH
authors.lastname: Lee
authors.forename: Damon
authors.initials: D
authors.lastname: Poburko
authors.forename: Kuo-Hsing
authors.initials: KH
authors.lastname: Kuo
authors.forename: Chun
authors.initials: C
authors.lastname: Seow
authors.forename: Cornelis
authors.initials: C
authors.lastname: van Breemen
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000502:physiology*
chemical_list: D000252:Calcium-Transporting ATPases