Single nonselective cation channels and Ca2+-activated K+ channels in aortic endothelial cells.
In cultured bovine aortic endothelial cells, elementary K+ currents were studied in cell-attached and inside-out patches using the standard patch-clamp technique. Two different cationic channels were found, a large channel with a mean unitary conductance of 150 +/- 10 pS and a small channel with a mean unitary conductance of 12.5 +/- 1.1 pS. The 150-pS channel proved to be voltage- and Ca2+-activatable and seems to be a K+ channel. Its open probability increased on membrane depolarization and, at a given membrane potential, was greatly enhanced by elevating the Ca2+ concentration at the cytoplasmic side of the membrane from 10(-7) to 10(-4) M. 150-pS channels were not influenced by the patch configuration in that patch excision neither induced run-down nor evoked channel activity in silent cell-attached patches. However, they were only seen in two out of 55 patches. The 12-pS channel was predominant, a nonselective cationic channel with almost the same permeability for K+ and Na+ whose open probability was minimal near -60 mV but increased on membrane hyperpolarization. An increase in internal Ca2+ from 10(-7) to 10(-4) M left the open probability unchanged. Although the K+ selectivity of the 150-pS channels remains to be elucidated, it is concluded that they may be involved in controlling Ca2+-dependent cellular functions. Under physiological conditions, 12-pS nonselective channels may provide an inward cationic pathway for Na+.
D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology
D007473:Ion Channels; D011188:Potassium; D002118:Calcium