Induction of Ca2+-activated K+ current and transient outward currents in human capillary endothelial cells.

Human capillary endothelial cells (HCEC) in normal media contain noninactivating outwardly rectifying chloride currents, TEA-sensitive delayed rectifier K+ currents and an inward rectifier K+ current. Two additional ionic currents are induced in HCEC when the media are allowed to become conditioned: A Ca2+-activated K+ current (BKCA) that is sensitive to iberiotoxin is induced in 23.5% of the cells, a transient 4-AP-sensitive K+ current (A current) is induced in 24.7% of the cells, and in 22.3% of the cells both the transient and BKCA currents are coinduced. The EC50 for Ca2+ activation of the BKCA current in HCEC from conditioned media is 213 nM. RNA message for BKCA (hSlo clone) is undetecable after PCR amplification in control cells but is seen in those from conditioned cells. The induction of BKCA current is not blocked by conditioning with inhibitors of nitric oxide synthase, cyclo-oxgenase or lypo-oxygenase pathways. Apparently the characteristics of human endothelial cells are highly malleable and can be easily modified by their local environment.