KATP channel blocking actions of quaternary ions play no role in their antiproliferative action on mouse leukaemia and rat vascular smooth muscle cells in vitro.
1. The aim of the present study was to investigate the possibility that, in the two cell lines examined, alterations in cell growth caused by lipophilic quaternary ions may involve KATP channels. We examined the effect of tetraphenylphosphonium (TPP), tetraphenylboron (TPB), rhodamine 123, dequalinium chloride (DECA) and the non-quaternary ion cisplatin on the proliferation of L1210 mouse leukaemia cells and rat smooth muscle cells in vitro. The KATP channel opener levcromakalim (LKM) and the KATP channel antagonist glibenclamide were also tested. 2. From growth-inhibition studies, the rank order of potency (based on pIC50 values) using L1210 leukaemia cells was: DECA (6.61) > cisplatin (6.09) = rhodamine 123 (6.01) > TPP (5.61) > TPB (4.25). Levcromakalim and glibenclamide were found to be inactive at the maximum concentrations used (100 mumol/L). A different rank order of potency was obtained in rat aortic smooth muscle cells: cisplatin (6.33) > DECA (5.67) > TPP (4.96) > rhodamine 123 (4.1). Tetraphenylboron (30 mumol/L), LKM (100 mumol/L) and glibenclamide (100 mumol/L) were found to be inactive. 3. When the negatively charged TPB (30 mumol/L) was combined with some of the active agents, the potency of the active agents was increased. Thus, in L1210 cells, rhodamine 123, DECA and TPP were all more potent at inhibiting cell growth in the presence of TPB. Tetraphenylboron had no effect on cisplatin in this cell line. In rat smooth muscle cells, TPB (30 mumol/L) potentiated the effect of rhodamine 123 but had no effect on the actions of cisplatin, DECA or TPP. 4. In functional studies, rhodamine 123 was a weak antagonist of the vasorelaxant responses to the KATP channel opener LKM in the porcine right circumflex artery in vitro. The pKB value obtained for rhodamine 123 at 100 mumol/L was 4.95. Dequalinium chloride was inactive. 5. We found no correlation between the actions of the compounds tested to antagonise KATP channels and their ability to inhibit cell proliferation. In addition, compounds known to regulate KATP channel activity failed to influence proliferative rates. These results suggest that KATP channels are not involved in the antiproliferative action of TPP and other quaternary ions in the two cell lines studied.
Piekarska
A E
AE
Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
Webster
L
L
Saltis
J
J
McPherson
G A
GA
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001011:Aorta / Q000166:cytology / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002945:Cisplatin / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D003868:Dequalinium / Q000494:pharmacology; D066298:In Vitro Techniques; D007939:Leukemia L1210 / Q000473:pathology*; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009861:Onium Compounds / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D026902:Potassium Channel Blockers; D051381:Rats; D020112:Rhodamine 123 / Q000494:pharmacology; D013552:Swine; D013775:Tetraphenylborate / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000970:Antineoplastic Agents; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D026902:Potassium Channel Blockers; D014662:Vasoconstrictor Agents; D020112:Rhodamine 123; D013775:Tetraphenylborate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000255:Adenosine Triphosphate; D003868:Dequalinium; D002945:Cisplatin; C013289:tetraphenylphosphonium