title: High-affinity [3H]choline accumulation in cultured human skin fibroblasts.
abstract: [3H]Choline can be transported across cell membranes by high-affinity (KT less than 5 microM) and low-affinity (KT much greater than 5 microM) systems. High-affinity choline accumulation (HACA) has been demonstrated in synaptosomes made from cholinergic brain regions such as the hippocampus and caudate-putamen. In cell culture, HACA has been demonstrated in glia and avian telencephalon, dissociated spinal cord, and muscle fibroblasts. We examined [3H]choline accumulation in a single normal human fibroblast line cultured from skin biopsy. [3H]Choline accumulation was temperature-dependent and linear with incubation time up to 6 min at 0.125 microM-choline. The apparent KT for [3H]choline was 5 microM, which is similar to that observed in avian fibroblasts. Isoosmotic replacement of Na+ with either Li+ (144 mM) or sucrose (288 mM) severely reduced [3H]choline accumulation (by 70-90%). Pre-incubation with ouabain (100 microM), sodium orthovanadate (100 microM), or 2,4-dinitrophenol (100 microM), or replacement of Ca2+ by Mg2+ had little or no effect on subsequent [3H]choline accumulation. [3H]Choline accumulation was inhibited by hemicholinium-3 (HC-3); after pre-incubation in HC-3 at 37 degrees C for 10 min, the IC50 (at 0.125 microM-choline) was 5.6 microM. The HC-3 sensitivity, Na+ dependence, and low KT suggest that human skin fibroblasts have a high-affinity transport system for choline.
mesh_terms: D000328:Adult; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D002794:Choline / Q000378:metabolism*; D004140:Dinitrophenols / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006426:Hemicholinium 3 / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D012867:Skin / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014316:Tritium
chemical_list: D004140:Dinitrophenols; D014316:Tritium; D006426:Hemicholinium 3; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D002794:Choline