Voltage-activated potassium, but not calcium currents in cultured bovine aortic endothelial cells

Abstract

The electrophysiological properties of cultured bovine aortic endothelial cells were characterized using the patch clamp technique. Resting potentials were measured on passing to the whole cell recording configuration and were close to--65 mV in healthy cells. In cell-attached recordings with a high potassium pipette solution, inward single channel currents were observed with zero applied pipette potential. A linear slope conductance of 25 pS was found for a wide range of hyperpolarizing patch potentials and also for depolarizing patch potentials of up to 50-60 mV. A pronounced inward rectification was apparent as no reversal of these currents was seen for larger depolarizations. Whole cell recording in physiological solutions revealed the presence of a hyperpolarization-activated inward current with strong inward rectification and no voltage-dependent ionic current was observed upon depolarization in this subset of cells. Substitution of potassium for external sodium resulted in a shift in the zero current potential consistent with potassium being the main permeant ion. Together with the characteristic voltage-dependent blocking actions of external sodium ions and low concentrations of barium and caesium ions, our results indicate that this current is very similar to the classical inward rectifier as originally described in skeletal muscle and in tunicate eggs. In a second population of cells, a depolarization-activated outward current displaying characteristics of the fast transient A-type potassium current as first reported in molluscan neurones was also observed. No evidence for inward voltage dependent sodium or calcium currents was found.

Ion Currents in Smooth Muscle Cells From Human Small Bronchioles: Presence of an Inward Rectifier K+ Current and Three Types of Large Conductance K+ Channel

“…The conductance of 17 pS is within the range of typical values for inward rectifier channels, and similar to that shown in endothelial cells (e.g. Takeda et al 1987;Hoyer et al 1991). …”

“…IDR was initially described in skeletal muscle and cardiac cells, and was later found in tunicate eggs and neurons (reviewed in Hille, 1992), as well as in cultured (Takeda et al 1987) and freshly dissociated (Hoyer et al 1991) endothelial cells. IIR is not regarded as a current typical for smooth muscle cells, and has so far only been described in smooth muscle from small arteries and arterioles in the cerebral and coronary circulations (Quayle et al 1993(Quayle et al , 1997Johnson et al 1998), although a low density of IIR has recently been reported in small renal arteries (Prior et al 1998).…”

Histamine‐induced inward currents in cultured endothelial cells from human umbilical vein

“…Firstly, the measured membrane potential was lower than that recently found by use of similar techniques in cultured bovine arterial endothelial cells (Takeda et al, 1987;Colden-Stanfield et al, 1987;Adams et al, 1987;Johns et al, 1987). However, similar low values of resting potentials have been reported in confluent endothelial cell cultures (Venter et al, 1975;Richter & Halle, 1983) and in intact tissue (Northover, 1980), where gap junctions and electrical coupling between cells can be expected to be present (Simionescu et al, 1975;Venter et al, 1975).…”

“…Experimental methods, data recording on FM tape (Bruel & Kjaer, Denmark) and offline computer (Labtam, Australia) analysis procedures are similar to those previously described elsewhere in detail (Bregestovski et al, 1986;Takeda et al, 1987). Pipettes for whole cell recording had resistances of 3-7 MO.…”

Effects of vasoactive agonists on the membrane potential of cultured bovine aortic and guinea‐pig coronary endothelium.

“…These findings suggest that the agonist-induced increase in transmembrane Ca2+ influx was much larger in aortic than in coronary endothelial cells. This conclusion is supported by spectrofluorometric (Indo-1) (Takeda, Schini & Stoeckel, 1987) with a negative slope between -50 and -25 mV (Cannell & Sage, 1989 (Daut et al 1988). The molecular mechanism underlying the negative slope of the current-voltage relation in BAECs may be a decrease in the open probability of the inwardly rectifying K+ channel with depolarization, as has been found in cardiac ventricular muscle (Kurachi, 1985).…”