title: Calcium signalling in smooth muscle.
abstract: Calcium signalling in smooth muscles is complex, but our understanding of it has increased markedly in recent years. Thus, progress has been made in relating global Ca2+ signals to changes in force in smooth muscles and understanding the biochemical and molecular mechanisms involved in Ca2+ sensitization, i.e. altering the relation between Ca2+ and force. Attention is now focussed more on the role of the internal Ca2+ store, the sarcoplasmic reticulum (SR), global Ca2+ signals and control of excitability. Modern imaging techniques have shown the elaborate SR network in smooth muscles, along with the expression of IP3 and ryanodine receptors. The role and cross-talk between these two Ca(2+) release mechanisms, as well as possible compartmentalization of the SR Ca2+ store are discussed. The close proximity between SR and surface membrane has long been known but the details of this special region to Ca2+ signalling and the role of local sub-membrane Ca2+ concentrations and membrane microdomains are only now emerging. The activation of K+ and Cl- channels by local Ca2+ signals, can have profound effects on excitability and hence contraction. We examine the evidence for both Ca2+ sparks and puffs in controlling ion channel activity, as well as a fundamental role for Ca2+ sparks in governing the period of inexcitability in smooth muscle, i.e. the refractory period. Finally, the relation between different Ca2+ signals, e.g. sparks, waves and transients, to smooth muscle activity in health and disease is becoming clearer and will be discussed.
authors.affiliation: Department of Physiology, The University of Liverpool, Liverpool L69 3BX, UK. s.wray@liv.ac.uk
authors.forename: Susan
authors.initials: S
authors.lastname: Wray
authors.forename: Theodor
authors.initials: T
authors.lastname: Burdyga
authors.forename: Karen
authors.initials: K
authors.lastname: Noble
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D018118:Chloride Channels / Q000502:physiology; D006801:Humans; D021962:Membrane Microdomains / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000502:physiology
chemical_list: D018118:Chloride Channels; D051640:Small-Conductance Calcium-Activated Potassium Channels