Electrophysiological studies of forskolin-induced changes in ion transport in the human colon carcinoma cell line HT-29 cl.19A: lack of evidence for a cAMP-activated basolateral K+ conductance.

摘要: Forskolin (i.e., cAMP)-modulation of ion transport pathways in filter-grown monolayers the Cl(-)-secreting subclone (19A) human colon carcinoma cell line HT29 was studied by combined Ussing chamber and microimpalement experiments. Changes electrophysiological parameters provoked serosal addition 10(-5) M forskolin included: (i) a sustained increase transepithelial potential difference (3.9 +/- 0.4 mV), (ii) transient decrease resistance with 26 3 omega.cm2 from mean value 138 13 before addition, (iii) depolarization membrane 24 1 mV resting -50 (iv) fractional apical 0.80 0.02 to 0.22 0.01. Both, changes resistance, persisted for at least 10 min were dependent on presence Cl- medium. Subsequent bumetanide (10(-4) M), an inhibitor Na/K/2Cl cotransport, reduced potential, induced repolarization small resistance. Serosal Ba2+ (1 mM), known basolateral K+ conductance, strongly electrical effects forskolin. No evidence found (cAMP)-induced modulation conductance. The results suggest that forskolin-induced secretion HT-29 cl.19A colonic mainly cAMP-provoked conductance but does not affect or pole cell. indicate capacity mechanism basal Ba(2+)-sensitive are sufficiently large maintain efflux across membrane. Furthermore, is presented anomalous inhibitory action putative channel blockers NPPB DPC rather than