Inwardly rectifying K+ channels in freshly dissociated coronary endothelial cells from guinea‐pig heart.

Abstract

1. Inwardly rectifying K+ ('K(IR)) currents of freshly dissociated coronary endothelial cells from guinea-pig heart were investigated with the perforated-patch technique. 2. The whole-cell current-voltage relationship of endothelial cells showed strong inward rectification. Increasing the extracellular K+ resulted in an increase of inward currents. The slope conductance of the cells in the potential range negative to the calculated potassium equilibrium potential (EK) with 5, 60 and 150 mm external potassium was 0-18 + 0'14, 0.55 + 0 50 and 0-63 + 0-29 nS (mean + S.D.), respectively. 3. To quantify the steepness of inward rectification, the voltage dependence of the chord conductance of the cells was fitted with a Boltzmann function. The slope factor k describing the steepness of the relationship was 6-8 + 1'5 mV. 4. Extracellular barium induced a potential-and time-dependent block of inward currents through endothelial KIR channels. Half-maximum inhibition of IK(IR) currents was achieved with < 1 AM barium at a membrane potential of -70 mV in a solution containing 60 mM K+.5. Whole-cell inward currents revealed the opening and closing of single KIR channels. The single-channel conductance was 26 + 3 pS with 60 mm external K+ and 33 + 6 pS with 150 mm external K+. 6. Our results suggest that the electrical properties of freshly dissociated endothelial cells are to a large extent determined by five to sixty active strong inwardly rectifying K+ (KIR) channels.

Effects of Increased Intracellular Cl− Concentration on Membrane Responses to Acetylcholine in the Isolated Endothelium of Guinea Pig Mesenteric Arteries

“…Because the variation in [Cl -] i slightly affected the resting membrane potential, some Cl -conductances might also contribute to the resting current. In a separate series of experiments, inward rectification observed at negative potentials was found to be abolished by Ba 2+ (100 µM), suggesting that these cells possessed inwardly rectifying K + channels, as described by many investigators (for example, see [23]). …”

Hyperpolarization of isolated capillaries from guinea‐pig heart induced by K+ channel openers and glucose deprivation

“…The mean resting potential of the coronary capillaries (−46 ± 4·2 mV) is in the range of the membrane potentials determined for endothelial cells of different origin (−20 to −85 mV; Adams et al 1989;Revest & Abott, 1992;He & Curry, 1995) and close to the membrane potential of endothelial cells of venular microvessels from the mesentery (−44 mV; He & Curry, 1994), freshly isolated microvascular endothelial cells (−35 ± 21 mV;von Beckerath et al 1996) and freshly isolated aortic endothelial cells (−20 to −50 mV; Katnik & Adams, 1995). The resting membrane potential of the capillaries often showed fluctuations.…”

“…Another factor that might contribute to the high potency of K¤ channel openers in coronary capillaries could be a high resting membrane resistance of these endothelial cells as indicated by the occurrence of membrane potential fluctuations. Mean values for the input resistances of microvascular coronary endothelial cells are 1·7 ± 0·4 GÙ (Daut, Mehrke, Nees & Newman, 1988) and •100 GÙ (von Beckerath, Dittrich, Klieber & Daut, 1996). Only a few KATP channels, and possibly only a small fraction of the KATP channels available, need to be activated to generate a hyperpolarization towards the K¤ equilibrium potential.…”

A mathematical model of plasma membrane electrophysiology and calcium dynamics in vascular endothelial cells

“…A1-A3 in the APPENDIX) (50). Maximal Kir conductance is described by an increasing function of [K ϩ ]o and fits well Kir conductance data from guinea pig coronary ECs (data not shown) (75). Equations A1-A3 were fitted to rat mesenteric EC Kir currentvoltage (I-V) data in the Ϫ100 to ϩ40 mV range ( Fig.…”