KATP channels regulate mitogenically induced proliferation in primary rat hepatocytes and human liver cell lines. Implications for liver growth control and potential therapeutic targeting.
To determine whether K(ATP) channels control liver growth, we used primary rat hepatocytes and several human cancer cell lines for assays. K(ATP) channel openers (minoxidil, cromakalim, and pinacidil) increased cellular DNA synthesis, whereas K(ATP) channel blockers (quinidine and glibenclamide) attenuated DNA synthesis. The channel inhibitor glibenclamide decreased the clonogenicity of HepG2 cells without inducing cytotoxicity or apoptosis. To demonstrate the specificity of drugs for K(+) channels, whole-cell patch-clamp recordings were made. Hepatocytes revealed K(+) currents with K(ATP) channel properties. These K(+) currents were augmented by minoxidil and pinacidil and attenuated by glibenclamide as well as tetraethylammonium, in agreement with established responses of K(ATP) channels. Reverse transcription of total cellular RNA followed by polymerase chain reaction showed expression of K(ATP) channel-specific subunits in rat hepatocytes and human liver cell lines. Calcium fluxes were unperturbed in glibenclamide-treated HepG2 cells and primary rat hepatocytes following induction with ATP and hepatocyte growth factor, respectively, suggesting that the effect of K(ATP) channel activity upon hepatocyte proliferation was not simply due to indirect modulation of intracellular calcium. The regulation of mitogen-related hepatocyte proliferation by K(ATP) channels advances our insights into liver growth control. The findings have implications in mechanisms concerning liver development, regeneration, and oncogenesis.
Malhi
H
H
Marion Bessin Liver Research Center, the Cancer Research Center, and the Departments of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Irani
A N
AN
Rajvanshi
P
P
Suadicani
S O
SO
Spray
D C
DC
McDonald
T V
TV
Gupta
S
S
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D019806:Cromakalim / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D004594:Electrophysiology; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D054086:KATP Channels; D007700:Kinetics; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development*; D008914:Minoxidil / Q000494:pharmacology; D008934:Mitogens / Q000494:pharmacology*; D020110:Pinacidil / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011802:Quinidine / Q000494:pharmacology; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018528:ATP-Binding Cassette Transporters; D054086:KATP Channels; D008934:Mitogens; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C092520:uK-ATP-1 potassium channel; D019806:Cromakalim; D008914:Minoxidil; D020110:Pinacidil; D011802:Quinidine; D005905:Glyburide; D002118:Calcium