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

Human capillary endothelial cells (HCEC) in normal media contain noninactiv ating outwardly rectifying chloride currents, TEA-sensitive delayed rectifi er K+ currents and an inward rectifier K+ current. Two additional ionic cur rents are induced in HCEC when the media are allowed to become conditioned: A Ca2+-activated K+ current (BKCA) that is sensitive to iberiotoxin is ind uced in 23.5% of the cells, a transient 4-AP-sensitive K+ current (A curren t) is induced in 24.7% of the cells, and in 22.3% of the cells both the tra nsient 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 BKC A (hSlo clone) is undetecable after PCR amplification in control cells but is seen in those from conditioned cells. The induction of BKCA current is n ot blocked by conditioning with inhibitors of nitric oxide synthase, cyclo- oxgenase or lypooxygenase pathways. Apparently the characteristics of human endothelial cells are highly malleable and can be easily modified by their local environment.