Regulation of chloride transport in cultured normal and cystic fibrosis keratinocytes.
Cultured normal (N) cystic fibrosis (CF) keratinocytes were evaluated for their Cl(-)-transport properties by patch-clamp-, Ussing chamber- and isotopic efflux-measurements. Special attention was paid to a 32 pS outwardly rectifying Cl- channel which has been reported to be activated upon activation of cAMP-dependent pathways in N, but not in CF cells. This depolarization-induced Cl- channel was found with a similar incidence in N and CF apical keratinocyte membranes. However, activation of this channel in excised patches by protein kinase (PK)-A or PK-C was not successful in either N or CF keratinocytes. Forskolin was not able to activate Cl- channels in N and CF cell-attached patches. The Ca(2+)-ionophore A23187 activated in cell-attached patches a linear 17 pS Cl- channel in both N and CF cells. This channel inactivated upon excision. No relationship between the cell-attached 17 pS and the excised 32 pS channel could be demonstrated. Returning to the measurement of Cl- transport at the macroscopic level, we found that a drastic rise in intracellular cAMP induced by forskolin did in N as well as CF cells not result in a change in the short-circuit current (Isc) or the fractional efflux rates of 36Cl- and 125I-. In contrast, addition of A23187 resulted in an increase of the Isc and in the isotopic anion efflux rates in N and CF cells. We conclude that Cl(-)-transport in cultured human keratinocytes can be activated by Ca2+, but not by cAMP-dependent pathways.
Kansen
M
M
Department of Cell Biology I and Genetics, Erasmus University, Rotterdam, Netherlands.
Keulemans
J
J
Hoogeveen
A T
AT
Scholte
B
B
Vaandrager
A B
AB
van der Kamp
A W
AW
Sinaasappel
M
M
Bot
A G
AG
de Jonge
H R
HR
Bijman
J
J
D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D002713:Chlorine; D003550:Cystic Fibrosis / Q000378:metabolism* / Q000473:pathology; D004553:Electric Conductivity; D006801:Humans; D007457:Iodine Radioisotopes; D007473:Ion Channels / Q000378:metabolism* / Q000502:physiology; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D011494:Protein Kinases / Q000494:pharmacology
D018118:Chloride Channels; D002712:Chlorides; D007457:Iodine Radioisotopes; D007473:Ion Channels; D008565:Membrane Proteins; D002713:Chlorine; D011494:Protein Kinases