We measured free intracellular @entity141 concentration ([ @entity141 ]i) and @entity141 current (ICa) simultaneously in voltage-clamped, indo-1-loaded smooth muscle cells isolated from the circular layer of the @entity235 antrum. Resting [ @entity141 ]i averaged 144 +/- 20 nM in cells held at -70 mV. Depolarization positive to -50 mV elicited ICa and increased [ @entity141 ]i. Peak [ @entity141 ]i occurred between 0 and +10 mV and averaged 372 +/- 48 nM. On repolarization, [ @entity141 ]i decreased slowly (time constant 2-3 s) and the rate depended on the magnitude of [ @entity141 ]i. Cells were also voltage clamped with protocols that mimicked the upstroke and plateau phases of slow waves. With simulated plateau potentials of -55 to -45 mV, [ @entity141 ]i increased transiently as a result of the small transient ICa elicited by the upstroke depolarization. Sustained ICa was of sufficient magnitude with plateau depolarizations positive to -40 mV to cause a secondary rise in [ @entity141 ]i throughout the plateau phase. These data suggest that at the plateau potential of slow waves in situ, ICa is sufficient to cause a sustained increase in [ @entity141 ]i. The resulting accumulation of @entity141 may couple the slow wave plateau to contraction and may increase the open probability of @entity141 -activated K channels. The latter may provide the outward current necessary to initiate repolarization.

Relationship between calcium current and cytosolic calcium in XXXX gastric smooth muscle cells.

@entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+', 'Ca(2+)'] @entity235 :: ('9615', 'Species') :: ['canine']
@entity235 :: (9615,Species) :: ['canine']
