title: Cl- channel blockers inhibit transition of quiescent (G0) fibroblasts into the cell cycle.
abstract: Modulation of ion permeability during the cell cycle is one of the key events in cell cycle progression. We have compared the effects of K+ and Cl- channel blockers on the cell cycle in synchronous and asynchronous NIH3T3 cells. The Cl- channel blocker 5-N-2-(3-phenylpropylamino) benzoic acid (NPPB; 0.2 mM) inhibited entry into S phase in synchronous cells but not in asynchronous cells, while the K+ channel blocker 4-aminopyridine (4-AP) showed similar inhibitory effects in both conditions. In NIH3T3 cells synchronized by serum deprivation/replenishment, G0-to-G1 transition occurred within 8 h after serum addition, and the G1/S checkpoint at 10-14 h. NPPB applied only at 0-8 or 8-14 h after serum addition inhibited entry into S phase. Cl- permeability measured as 125I efflux increased at 4 and 10 h after serum addition. Ki-67-negative cells, which represent quiescent G0 phase cells, progressively decreased in number until 8 h after serum addition. The Cl- channel blockers (NPPB and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid [DIDS]) but not the K+ channel blocker (4-AP) significantly decreased the rate of reduction in number of Ki-67-negative cells. These data indicate that an increase in Cl- permeability plays an important role in reentry of quiescent cells into the proliferating phase, in addition to the known effects on passage through the G1/S checkpoint.
authors.affiliation: Department of Physiology, Akita University School of Medicine, Akita, Japan.
authors.forename: Ya-Juan
authors.initials: YJ
authors.lastname: Zheng
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Furukawa
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Tajimi
authors.forename: Nobuya
authors.initials: N
authors.lastname: Inagaki
mesh_terms: D016475:3T3 Cells; D015761:4-Aminopyridine / Q000494:pharmacology; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D018118:Chloride Channels / Q000037:antagonists & inhibitors*; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D007457:Iodine Radioisotopes; D019394:Ki-67 Antigen / Q000032:analysis; D051379:Mice; D009579:Nitrobenzoates / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D016192:Resting Phase, Cell Cycle / Q000187:drug effects*; D016196:S Phase / Q000187:drug effects
chemical_list: D020533:Angiogenesis Inhibitors; D001798:Blood Proteins; D018118:Chloride Channels; D007457:Iodine Radioisotopes; D019394:Ki-67 Antigen; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D015761:4-Aminopyridine