A Na(+)-sensitive cation channel modulated by angiotensin II in cultured intestinal myocytes.
Single-channel currents were recorded in excised inside-out and cell-attached patches of cultured cells from the longitudinal smooth muscle of the guinea pig ileum. In the presence of symmetrical high-K+ solutions, we identified a voltage-dependent 12-pS channel. It was reversibly blocked by addition of either Ba2+ or Cs+ at the cellular side of the patch but was insensitive to Ca2+ or ATP. This channel had poor selectivity concerning cations (PLi > PK = PNa = PCa, where P is permeability) and low permeability to anions. Isosmotic substitution of NaCl for KCl in the solution facing the cellular side enhanced the channel activity by increasing NPo values where N is number of channels and Po is open probability. In the cell-attached configuration, the channel was also activated by addition of angiotensin II in the bath solution. We propose that this nonselective cation channel might play a role in the control of the membrane potential during the contractile response of the guinea pig ileum to agonists by keeping the voltage-sensitive Ca2+ channels open.
Nouailhetas
V L
VL
Department of Biophysics, Escola Paulista de Medicina, São Paulo, Brazil.
Aboulafia
J
J
Frediani-Neto
E
E
Ferreira
A T
AT
Paiva
A C
AC
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002412:Cations / Q000378:metabolism*; D002478:Cells, Cultured; D004594:Electrophysiology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000166:cytology / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D010539:Permeability; D012964:Sodium / Q000494:pharmacology*
D002412:Cations; D007473:Ion Channels; D000804:Angiotensin II; D012964:Sodium