title: Spermidine decreases Na⁺,K⁺-ATPase activity through NMDA receptor and protein kinase G activation in the hippocampus of rats.
abstract: Spermidine is an endogenous polyamine with a polycationic structure present in the central nervous system of mammals. Spermidine regulates biological processes, such as Ca(2+) influx by glutamatergic N-methyl-d-aspartate receptor (NMDA receptor), which has been associated with nitric oxide synthase (NOS) and cGMP/PKG pathway activation and a decrease of Na(+),K(+)-ATPase activity in rats' cerebral cortex synaptosomes. Na(+),K(+)-ATPase establishes Na(+) and K(+) gradients across membranes of excitable cells and by this means maintains membrane potential and controls intracellular pH and volume. However, it has not been defined whether spermidine modulates Na(+),K(+)-ATPase activity in the hippocampus. In this study we investigated whether spermidine alters Na(+),K(+)-ATPase activity in slices of hippocampus from rats, and possible underlying mechanisms. Hippocampal slices and homogenates were incubated with spermidine (0.05-10 μM) for 30 min. Spermidine (0.5 and 1 μM) decreased Na(+),K(+)-ATPase activity in slices, but not in homogenates. MK-801 (100 and 10 μM), a non-competitive antagonist of NMDA receptor, arcaine (0.5μM), an antagonist of the polyamine binding site at the NMDA receptor, and L-NAME (100μM), a NOS inhibitor, prevented the inhibitory effect of spermidine (0.5 μM). ODQ (10 μM), a guanylate cyclase inhibitor, and KT5823 (2 μM), a protein kinase G inhibitor, also prevented the inhibitory effect of spermidine on Na(+),K(+)-ATPase activity. Spermidine (0.5 and 1.0 μM) increased NO(2) plus NO(3) (NOx) levels in slices, and MK-801 (100 μM) and arcaine (0.5 μM) prevented the effect of spermidine (0.5 μM) on the NOx content. These results suggest that spermidine-induced decrease of Na(+),K(+)-ATPase activity involves NMDA receptor/NOS/cGMP/PKG pathway.
authors.affiliation: Department of Chemistry, Center of Exact and Natural Sciences, Universidade Federal de Santa Maria, Santa Maria, RS 97105-900, Brazil.
authors.forename: Fabiano B
authors.initials: FB
authors.lastname: Carvalho
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Mello
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Marisco
authors.forename: Raquel
authors.initials: R
authors.lastname: Tonello
authors.forename: Bruna A
authors.initials: BA
authors.lastname: Girardi
authors.forename: Juliano
authors.initials: J
authors.lastname: Ferreira
authors.forename: Mauro S
authors.initials: MS
authors.lastname: Oliveira
authors.forename: Maribel A
authors.initials: MA
authors.lastname: Rubin
mesh_terms: D000818:Animals; D001645:Biguanides / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013095:Spermidine / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D001645:Biguanides; D002227:Carbazoles; D010069:Oxadiazoles; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; C073601:KT 5823; D009569:Nitric Oxide; C006624:arcaine; D016291:Dizocilpine Maleate; D019001:Nitric Oxide Synthase; D017869:Cyclic GMP-Dependent Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D006152:Cyclic GMP; D013095:Spermidine; D019331:NG-Nitroarginine Methyl Ester