Voltage-gated Ca entry in isolated bovine capillary endothelial cells: evidence of a new type of BAY K 8644-sensitive channel.
Isolated bovine capillary endothelial cells have been examined for voltage-dependent Ca entry. All cells displayed a low threshold activity, with the main characteristics of a T-type transient current, when examined using whole-cell recording for activation and inactivation and cell-attached conditions or inside-out patches for the elementary conductance (8 pS). 25% of the cells displayed an additional sustained current in 5 mM CaCl2 above -40 mV, which was enhanced by application of BAY K 8644, but almost insensitive to superfusion with nicardipine. Two types of channels (2.8 and 21 pS, in 110 mM BaCl2) were shown to have a BAY K 8644 sensitivity. The large conductance channels were L-type channels. The smaller events were elicited at more hyperpolarized potentials (by some 30 mV). Their mean open time was 16 ms in control conditions. In presence of BAY K 8644, additional long open times were observed (up to 100 ms as compared to 7.8 ms for the time constants of the slow mode of the L-type channel). We refer to these channels as SB channels: of small conductance and sensitive to BAY K 8644. In the presence of nicardipine, SB channels are not noticeably modified, in contrast to the L-type openings which are abolished. Also, SB open times are close to control values when nicardipine is added after a BAY K 8644 application. We suggest that, at physiological concentrations of divalent ions, an SB-type activity is elicited above -40 mV which generates the low threshold sustained current.
Bossu
J L
JL
Laboratoire d'Etude des Régulations Physiologiques, CNRS, Université Louis Pasteur, Strasbourg, France.
Elhamdani
A
A
Feltz
A
A
Tanzi
F
F
Aunis
D
D
Thierse
D
D
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000313:Adrenal Medulla / Q000098:blood supply*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002196:Capillaries; D002417:Cattle; D002469:Cell Separation; D002478:Cells, Cultured; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D015640:Ion Channel Gating
D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium