title: Polyamine uptake in cultured astrocytes: characterization and modulation by protein kinases.
abstract: The properties and regulation of the polyamine transport system in brain are still poorly understood. The present study shows, for the first time, the existence of a polyamine transport system in cerebellar astrocytes and suggests that polyamine uptake is mediated by a single and saturable high-affinity transport system for putrescine, spermine, and spermidine (K:(m) = 3.2, 1.2, and 1.8 microM:, respectively). Although substitution of NaCl by choline chloride produced a decrease in the putrescine, spermine, and spermidine uptake, it seems that polyamine transport in cerebellar astrocytes is not mediated by an Na(+) cotransport as in the presence of Na(+) and cholinium, polyamine uptake was much lower than when measured in a sucrose-based medium. On the other hand, ouabain, gramicidin (a Na(+) ionophore), and ionomycin (a Ca(2+) ionophore) produced a strong inhibition of polyamine uptake, suggesting that membrane potential could have an important role in the functioning of the astroglial polyamine uptake system. Moreover, protein kinase C inhibition produced an enhancement of polyamine uptake, whereas stimulation of protein kinase C with phorbol esters inhibited polyamine uptake. Alternatively, the tyrosine kinase inhibitor genistein caused a marked reduction in the uptake. No effects on polyamine uptake were observed with inhibitors and activators of cyclic AMP-dependent protein kinase or when Ca(2+)/calmodulin-dependent protein kinase II was inhibited with KN-62. These results suggest that the polyamine uptake system in cerebellar astrocytes could be modulated by protein kinase C and tyrosine kinase activities.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Universidad Autónoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Dot
authors.forename: M
authors.initials: M
authors.lastname: Lluch
authors.forename: I
authors.initials: I
authors.lastname: Blanco
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Alvarez
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001667:Binding, Competitive / Q000187:drug effects; D015317:Biogenic Polyamines / Q000378:metabolism / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism* / Q000494:pharmacology; D011700:Putrescine / Q000378:metabolism / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013095:Spermidine / Q000378:metabolism / Q000493:pharmacokinetics; D013096:Spermine / Q000378:metabolism / Q000493:pharmacokinetics; D013696:Temperature; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D015317:Biogenic Polyamines; D004791:Enzyme Inhibitors; D007476:Ionophores; D047428:Protein Kinase Inhibitors; D013096:Spermine; D012964:Sodium; D011494:Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D013755:Tetradecanoylphorbol Acetate; D013095:Spermidine; D011700:Putrescine