RENAL-CELLS TRANSFORMED WITH SV40 CONTAIN A HIGH-CONDUCTANCE CALCIUM-INSENSITIVE POTASSIUM CHANNEL

The inside-out variant of the patch-clamp technique was used to invest igate the properties of a K+ channel occurring in 20% of patches from two renal cell lines transformed with the wild-type simian virus 40 (S V40) (Vandewalle et al. J. Cell. Physiol. 141: 203-221, 1989). This ch annel was practically absent from the primary cultures of renal cortic al cells from which the cell lines were originally derived. With ident ical K+-rich solutions on both sides of the membrane patch, the channe l showed an inwardly rectifying current-voltage relationship with unit conductances of 151.8 +/- 4.8 pS at negative and 86.4 +/- 5.9 pS at p ositive voltages (n = 18). When K+ in the bath was replaced by Na+, a mean reversal potential of 57.0 +/- 5.2 mV (n = 6) was observed from w hich a K+-to-Na+ permeability ratio of 13 was calculated. The channel was insensitive to internal Ca2+ and was blocked by internal Ba2+. No clear dependence on voltage was apparent. This channel bears no resemb lance to any epithelial K+ channel and may be a novel type of K+ chann el. Its occurrence in two transformed cell lines with quite distinct p henotypes, one of proximal cells (RC.SV1) and the other of thick ascen ding limb cells (RC.SV2), suggests that transformation by SV40 might b e responsible for its appearance.