RESUMO
A sodium dependent GABA uptake system has been found in bovine adrenal medulla slices. This uptake has a Km of 83.19 +/- 38.45 microM and a Vmax of 9.20 +/- 1.36 pmol/min X mg of tissue. It was inhibited by nipecotic acid and 2,4-diaminobutyric acid (IC50 67 and 38.5 microM, respectively) but not by beta-alanine at concentrations up to 5 mM, a result which is similar to those found for the neuronal GABA uptake rather than the glial uptake. It is suggested that GABA uptake together with catabolic action of GABA-transaminase, also found in this tissue, could be regulating the GABA levels disposable for the proposed modulator role on catecholamine secretion of this amino acid in adrenal medulla.
Assuntos
Medula Suprarrenal/metabolismo , Prolina/análogos & derivados , Ácido gama-Aminobutírico/metabolismo , Aminobutiratos/farmacologia , Animais , Bovinos , Glucose/farmacologia , Cinética , Ácidos Nipecóticos/farmacologia , Potássio/farmacologia , Sódio/metabolismo , Fatores de Tempo , beta-Alanina/farmacologiaRESUMO
Methodologic and kinetic properties of gamma-aminobutyric acid (GABA) binding were studied in platelet materials of different nature. Platelet GABA binding was saturable and specific. LiCl and RbCl added in vitro at concentration of 0.01 mM increased significantly platelet GABA binding. This activator effect, and its kinetic characteristics were different from those obtained for GABA uptake and 5-hydroxytryptamine (5-HT) binding, which suggest that the three processes are different in platelets.
Assuntos
Plaquetas/efeitos dos fármacos , Cloretos/farmacologia , Lítio/farmacologia , Rubídio/farmacologia , Ácido gama-Aminobutírico/metabolismo , Adulto , Sítios de Ligação , Feminino , Humanos , Cinética , Cloreto de Lítio , Masculino , Pessoa de Meia-Idade , Receptores de Superfície Celular/efeitos dos fármacos , Receptores de Superfície Celular/metabolismo , Receptores de GABA-A , Serotonina/metabolismo , Ácido gama-Aminobutírico/sangueRESUMO
The methodologic and kinetic characteristics of GABA uptake by platelets were determined in blood platelets of volunteer donors. Extrapolation of a reciprocal plot indicate two uptake systems: a high affinity and a passive diffusion mechanism. When LiCl and RbCl were added in vitro, they had no effect on platelet GABA uptake. Our data suggest that platelet GABA and 5-HT uptake are carried out by different systems.