Influence of internal calcium stores on calcium-activated membrane currents in smooth muscle.
Agonist-induced activation of second messenger systems that increase inositol 1,4,5-trisphosphate concentration plays an important role in the mobilisation of stored Ca2+ in smooth muscle. Release of Ca2+ which occurs spontaneously or by agonist stimulation causes activation of Ca(2+)-sensitive currents. Experiments using selective modulators of the Ca2+ uptake and release mechanisms of the sarcoplasmic reticulum provide evidence that depletion of the internal Ca2+ store triggers an influx of Ca2+ from the extracellular space. Recent data suggest that pool depletion causes the opening of non-selective cation channels which are possibly similar to those previously designated 'receptor-operated Ca2+ channels'. Ca2+ entry through these channels not only refills the internal Ca2+ pool, but also modulates membrane excitability by stimulating Ca(2+)-activated currents.
Low
A M
AM
Department of Biomedical Sciences, McMaster University, Hamilton, Canada.
Lang
R J
RJ
Daniel
E E
EE
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002463:Cell Membrane Permeability; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D008566:Membranes / Q000502:physiology; D009130:Muscle, Smooth / Q000378:metabolism / Q000502:physiology*; D009994:Osmolar Concentration; D012508:Sarcolemma / Q000378:metabolism; D015290:Second Messenger Systems
D007473:Ion Channels; D000252:Calcium-Transporting ATPases; D002118:Calcium