title: Verapamil inhibits the glucose transport activity of GLUT1.
abstract: Calcium channel blocker toxicity has been associated with marked hyperglycemia responsive only to high-dose insulin therapy. The exact mechanism(s) of this induced hyperglycemia has not been clearly delineated. The glucose transporter GLUT1 is expressed in a wide variety of cell types and is largely responsible for a basal level of glucose transport. GLUT1 also is activated by cell stress. The specific purpose of this study was to investigate the effects of the calcium channel blocker verapamil on the glucose uptake activity of GLUT1 in L929 fibroblasts cells. Dose-dependent effects of verapamil on glucose uptake were studied using L929 fibroblast cells with 2-deoxyglucose. Verapamil had a dose-dependent inhibitory effect on both basal and stress-activated transport activity of GLUT1. Basal activity was inhibited 50% by 300 μM verapamil, while 150 μM verapamil completely inhibited the activation induced by the stress of glucose deprivation. These effects were reversible and required verapamil to be present during the stress. Alteration of calcium concentrations by addition of 5 mM CaCl₂ or 4 mM EDTA had no effect on verapamil action. This study reveals the unique finding that verapamil has inhibitory effects on the transport activity of GLUT1 independent of its effects on calcium concentrations. The inhibition of GLUT1 may be one of the contributing factors to the hyperglycemia observed in CCB poisoning.
authors.affiliation: Department of Chemistry & Biochemistry, Calvin College, Grand Rapids, MI, USA.
authors.forename: Larry L
authors.initials: LL
authors.lastname: Louters
authors.forename: Nathan
authors.initials: N
authors.lastname: Stehouwer
authors.forename: Janelle
authors.initials: J
authors.lastname: Rekman
authors.forename: Andrew
authors.initials: A
authors.lastname: Tidball
authors.forename: Alexandra
authors.initials: A
authors.lastname: Cok
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Holstege
mesh_terms: D000818:Animals; D000963:Antimetabolites; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002122:Calcium Chloride / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000172:deficiency; D051272:Glucose Transporter Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D006943:Hyperglycemia / Q000097:blood; D051379:Mice; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D000963:Antimetabolites; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D051272:Glucose Transporter Type 1; C495678:Slc2a1 protein, mouse; D003847:Deoxyglucose; D004492:Edetic Acid; D014700:Verapamil; D005947:Glucose; D002122:Calcium Chloride