title: Cellular transport processes of aminoguanidine, a nitric oxide synthase inhibitor, in the opossum kidney cell culture line.
abstract: Aminoguanidine has potential pharmacologic utility for diabetes and nitric oxide - mediated inflammation. Because aminoguanidine is positively charged at physiologic pH (pK(a) approximately 10), it is unlikely that simple diffusion is a predominant mechanism for cellular penetration. This study sought to determine the transport processes by which aminoguanidine, a cationic compound, traverses across cellular membranes. In cultured opossum kidney (OK) cell monolayers, aminoguanidine transport involved both saturable and non-saturable diffusion processes. At passage numbers below 67, the observed V(max) and K(m) for saturable influx were significantly lower than that observed at passages greater than 79 (V(max): low passage, 21.2+/-7.8 pmol/(min*mg protein), n=3; versus high passage, 129.7+/-24.3 pmol/(min*mg protein), n=3, P<0.05; K(m): low passage, 23.7+/-10.8 microM, n=3; versus high passage, 101.7+/-5.6 microM, n=3, P<0.05; mean+/-S.E.M.). Nonsaturable processes were not statistically different (k(ns): low passage, 1.6+/-0.1 pmol/(min*mg protein*microM), n=3; high passage, 1.1+/-0.2 pmol/(min*mg protein*microM) n=3). Saturable influx was temperature dependent, and independent of ATP energy, sodium gradients or changes in membrane potential. Other organic cations competitively inhibited and trans-stimulated saturable influx. Aminoguanidine influx was increased in the presence of an outwardly-directed proton gradient and was inhibited in the presence of an inwardly-directed proton gradient. Correspondingly, aminoguanidine efflux was trans79) express a saturable, bi-directional carrier-mediated process to transport aminoguanidine across cellular membranes.
authors.affiliation: Department of Pharmaceutics, H517 Cooke-Hochstetter, School of Pharmacy, University at Buffalo, State University of New York, Buffalo, NY 14260, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Mahar Doan
authors.forename: S
authors.initials: S
authors.lastname: Ng
authors.forename: K M
authors.initials: KM
authors.lastname: Boje
mesh_terms: D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D006146:Guanidines / Q000493:pharmacokinetics*; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009893:Opossums; D013379:Substrate Specificity; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D006146:Guanidines; D013757:Tetraethylammonium Compounds; D019001:Nitric Oxide Synthase; C004479:pimagedine