Premium
Uptake of Agmatine into Rat Brain Synaptosomes: Possible Role of Cation Channels
Author(s) -
Sastre Magdalena,
Regunathan Soundararajan,
Reis Donald J.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.69062421.x
Subject(s) - agmatine , imidazoline receptor , arginine decarboxylase , chemistry , arginine , extracellular , idazoxan , polyamine , monoamine neurotransmitter , biochemistry , biophysics , amino acid , pharmacology , receptor , biology , antagonist , prazosin , serotonin
Agmatine (decarboxylated arginine), an endogenous ligand for imidazoline receptors, has been identified in brain where it is synthesized from arginine by arginine decarboxylase. Here we report a mechanism for the transport of agmatine into rat brain synaptosomes. The uptake of agmatine was energy‐ and temperature‐dependent and saturable with a K m of 18.83 ± 3.31 m M and a V max of 4.78 ± 0.67 nmol/mg of protein/min. Treatment with ouabain (Na + ,K + ‐ATPase inhibitor) or removal of extracellular Na + did not attenuate the uptake rate. Agmatine transport was not inhibited by amino acids, polyamines, or monoamines, indicating that the uptake is not mediated by any amino acid, polyamine, or monoamine carriers. When we examined the effects of some ion‐channel agents on agmatine uptake, only Ca 2+ ‐channel blockers inhibited the uptake, whereas a reduction in extracellular Ca 2+ increased it. In addition, some imidazoline drugs, such as idazoxan and phentolamine, were strong noncompetitive inhibitors of agmatine uptake. Thus, a selective, Na + ‐independent uptake system for agmatine exists in brain and may be important in regulating the extracellular concentration of agmatine.