title: Classification of ion channels in the luminal and abluminal membranes of guinea-pig endocardial endothelial cells.
abstract: 1. The ion channels on both the luminal and abluminal membranes of endocardial endothelial (EE) cells were separately recorded using the patch clamp technique in the guinea-pig heart. 2. The major population consisted of two types of non-selective cation channels, which showed open probabilities of 0.21 and 0.33 at the resting potential, and conductances of 36 and 11 pS, respectively. 3. The next major class was Cl- channels with an ohmic conductance of 409 pS. The channel was quiescent in the cell-attached mode but was activated by strong depolarization after excising the patch membrane. 4. The channels activated by intracellular Ca2+ were mainly K+ channels showing a 34 pS slope conductance and, less frequently, Ca(2+)-dependent K+ channels having a large conductance (210 pS). The inward rectifier K+ channel (32 pS) was also observed. 5. The non-selective cation channels were recorded on the luminal membrane, but scarcely on the abluminal membrane, suggesting an active transport of K+ and Na+ across the endocardium. 6. The resting membrane conductance of the EE cells may be provided mostly by non-selective cation channels and 34 pS Ca(2+)-dependent K+ channels.
authors.affiliation: Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Manabe
authors.forename: H
authors.initials: H
authors.lastname: Ito
authors.forename: H
authors.initials: H
authors.lastname: Matsuda
authors.forename: A
authors.initials: A
authors.lastname: Noma
authors.forename: Y
authors.initials: Y
authors.lastname: Shibata
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D004699:Endocardium / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004727:Endothelium / Q000378:metabolism; D006168:Guinea Pigs; D007473:Ion Channels / Q000145:classification* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D015221:Potassium Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium