Pharmacological and molecular characterization of ATP-sensitive K+ channels in the TE671 human medulloblastoma cell line.
ATP-sensitive K+ (K(ATP)) channels in the human medulloblastoma TE671 cell line were characterized by membrane potential assays utilizing a potentiometric fluorescent probe, bis-(1,3-dibutylbarbituric acid)trimethine oxonol (DiBAC4(3)), and by mRNA analysis. Membrane potential assays showed concentration-dependent and glyburide-sensitive changes in fluorescence upon addition of (-)-cromakalim, pinacidil, diazoxide and P1075. The rank order of potency for these openers was P1075 > (-)-cromakalim approximately = pinacidil > diazoxide. Additionally, glyburide and glipizide inhibited P1075-evoked responses in TE671 cells with half-maximal inhibitory concentrations of 0.22 and 14 microM, respectively. The rank order potencies of both openers and inhibitors were similar to those observed in the rat smooth muscle A-10 cell line. In contrast, in the rat pancreatic insulinoma RIN-m5F cell line, only diazoxide was effective as an opener. Reverse transcription-polymerase chain reaction (RT-PCR) studies detected sulfonylurea receptors SUR2B and SUR1 mRNA in TE671 cells whereas only SUR2B and SUR1 mRNA were, respectively, detected in A-10 and RIN-m5F cells. The inward rectifier Kir6.2 mRNA was detected in all three cell types whereas Kir6.1 was detected only in A-10 cells. Collectively, the molecular and pharmacologic studies suggest that K(ATP) channels endogenously expressed in TE671 medulloblastoma resemble those present in the smooth muscle.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001463:Barbiturates; D002478:Cells, Cultured; D019806:Cromakalim / Q000494:pharmacology; D005456:Fluorescent Dyes; D005470:Fluorometry; D005913:Glipizide / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D007340:Insulinoma / Q000737:chemistry; D007555:Isoxazoles; D008527:Medulloblastoma / Q000737:chemistry*; D008564:Membrane Potentials / Q000187:drug effects*; D009130:Muscle, Smooth / Q000737:chemistry; D010276:Parasympatholytics / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000145:classification* / Q000187:drug effects / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured