ATP-induced rise in apamin-sensitive Ca(2+)-dependent K+ conductance in adult rat hepatocytes.
Exogenous ATP-induced transient outward currents (IATP) were investigated in isolated adult rat hepatocytes using conventional whole cell patch and nystatin perforated patch recording modes. The IATP increased in a sigmoidal fashion with an increase in ATP concentration, where the half-maximal concentration was 1.4 microM. The order of current potency was 2-methylthio-ATP > or = UTP = ATP > > alpha, beta-methylene-ATP. IATP was depressed in a concentration-dependent manner by suramin and apamin. IATP reversed its direction at the K+ equilibrium potential. IATP occurred easily in hepatocytes obtained from female rats weighing > 250 g. Removal of extracellular Ca2+ had no effect on the peak amplitude of IATP, but thapsigargin abolished it. Intracellular perfusion with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, heparin, guanosine 5'-O-(3-thiotriphosphate), or neomycin also abolished IATP. Pretreatment with pertussis toxin or calmodulin antagonists had no effect on IATP. It was concluded that ATP binding to both P2Y and P2U purinoceptors coupled to G protein may raise apaminsensitive Ca(2+)-dependent K+ conductance via a phospholipase C-inositol trisphosphate-Ca2+ signaling pathway.
Yamashita
Y
Y
Department of Physiology, Kyushu University Faculty of Medicine, Fukuoka, Japan.
Ogawa
H
H
Akaike
N
N
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000375:Aging / Q000502:physiology; D000818:Animals; D001030:Apamin / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D004553:Electric Conductivity; D007425:Intracellular Membranes / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D058914:Purinergic Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D015398:Signal Transduction
D002147:Calmodulin; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D058914:Purinergic Antagonists; D001030:Apamin; D000255:Adenosine Triphosphate; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium