Beta-angonists modulate ACh-inhibition of a K current in intestinal smooth muscle cells.
ACh causes a long-lasting inhibition of STOCs via G proteins in intestinal smooth muscle cells. We examined the effects of isoproterenol (Iso) on the ACh-induced inhibition of STOCs in isolated ileal smooth muscle cells using the G omega-seal whole cell clamp technique. In control, ACh (1 microM) completely suppressed STOCs, which did not desensitize over a period lasting 20 minutes. When Iso (10 microM) was added to the bath in the presence of ACh, the ACh-induced inhibition of STOCs was gradually removed. This effect of Iso was prevented by propranolol (10 microM). Application of Db-cAMP (500 microM) mimicked the Iso effects. Intracellulary applied GTP-gamma S (100 microM) gradually suppressed STOCs in the absence of ACh, which could not be removed by either Iso or Db-cAMP. These results suggest that beta-adrenergic stimulation causes a removal of the muscarinic inhibition of STOCs via a cAMP-dependent process.
Shimada
T
T
2nd Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Hamada
E
E
Terano
A
A
Sugimoto
T
T
Kurachi
Y
Y
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity / Q000187:drug effects; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology*; D011817:Rabbits
D015221:Potassium Channels; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D003994:Bucladesine; D011433:Propranolol; D007545:Isoproterenol; D000109:Acetylcholine