Regenerative component of slow waves in the guinea-pig gastric antrum involves a delayed increase in [Ca(2+)](i) and Cl(-) channels.
Regenerative potentials were initiated by depolarizing short segments of single bundles of circular muscle isolated from the gastric antrum of guinea-pigs. When changes in [Ca(2+)](i) and membrane potential were recorded simultaneously, regenerative potentials were found to be associated with an increase in [Ca(2+)](i), with the increase starting after a minimum latency of about 1 s. Although the increase in [Ca(2+)](i) was reduced by nifedipine, the amplitudes of the regenerative responses were little changed. Regenerative responses and associated changes in [Ca(2+)](i) were abolished by loading the preparations with the Ca(2+) chelator MAPTA-AM. Regenerative potentials were abolished by 2-aminoethoxydiphenyl borate (2APB), an inhibitor of IP(3) induced Ca(2+) release, by N-ethylamaleimide (NEM), an alkylating agent which blocks activation of G-proteins and were reduced in amplitude by two agents which block chloride (Cl(-))-selective channels in many tissues. The observations suggest that membrane depolarization triggers IP(3) formation. This causes Ca(2+) release from intracellular stores which activates Ca(2+)-dependent Cl(-) channels.
Hirst
G D S
GD
Department of Zoology, University of Melbourne, Victoria 3010, Australia. d.hirst@zoology.unimelb.edu.au
Bramich
N J
NJ
Teramoto
N
N
Suzuki
H
H
Edwards
F R
FR
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D011706:Pyloric Antrum / Q000502:physiology; D011930:Reaction Time; D012038:Regeneration / Q000187:drug effects / Q000502:physiology
D015220:Calcium Channels; D002614:Chelating Agents; D018118:Chloride Channels; D004533:Egtazic Acid; C058180:5,5'-dimethyl-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate; D009543:Nifedipine