Extracción de metabolitos ácidos durante el análisis de catecolaminas en tejido cerebral de ratas / Extraction of acid metabolites during the analysis of catecholamines in rat brain tissue / Extração de metabólitos ácidos durante a análise de catecolaminas no tecido cérebro de rato

A través del método de equilibrio batch se comparó la adsorción de las catecolaminas Dopamina (DA), Noradrenalina (NA) y Adrenalina (A), y de los metabolitos ácido dihidroxifenilacético (Dopac) y ácido indolacético (5- HIAA) en las fases sólidas octadecil (C18) hidrofóbica, diol (C Diol) hidrofílica y de intercambio catiónico débil (WCX). En la fase sólida WCX a pH 4,0 se observó un 78% de adsorción de catecolaminas y 68% de adsorción de Dopac. Las isotermas de adsorción de las catecolaminas en la fase WCX son de tipo Langmuir. La adrenalina tiene mayor afinidad que la dopamina por la fase WCX a pH 4,0 y la dopamina mayor afinidad que el Dopac y éste es coadsorbido sobre las catecolaminas adsorbidas en la fase WCX. Un ensayo con solventes orgánicos demostró que el tolueno extrajo selectivamente de una mezcla sintética el Dopac y el 5-HIAA coadsorbido, mientras que en una muestra de tejido cerebral de ratas experimentales fueron extraídos el Dopac y el ácido homovanílico (HVA). Estos resultados sirvieron para proponer un paso adicional de extracción con solventes orgánicos para la separación de metabolitos ácidos durante la extracción en fase sólida (EFS) en el análisis de catecolaminas.

The adsorptions of Dopamine (DA), Noradrenaline (NA), and Adrenaline (A) catecholamines were compared by using the batch equilibrium method, as well as those of the dihydroxyphenylacetic acid (Dopac) and indolacetic acid (5-HIAA) metabolites on the hydrophobic octadecyl (C18), hydrophilic diol (C Diol) and weak cation exchange (WCX) solid phases. On the WCX solid phase at pH 4.0, catecholamines adsorption of 78% and Dopac adsorption of 68% were observed. The adsorption isotherms of catecholamines on the for the WCX phase at pH 4.0 than dopamine, dopamine has greater affinity than Dopac, and this latter is coadsorbed over the adsorbed catecholamines on the WCX phase. A trial with organic solvents demonstrated that toluene selectively extracted Dopac and the coadsorbed 5-HIAA from a synthetic mix, while in a brain tissue specimen from experimental rats, Dopac and homovanilic acid (HVA) were extracted. These results served to propose an additional extraction step with organic solvents throughout the separation of acid metabolites during solid phase extraction (EFS) for the analysis of catecholamines.

Evidence for a role of beta-endorphin in activity of nigrostriatal neurons in the rat

The effects of icv administration of ß-endorphin on secretory activity of dopaminergic neurons is described. Homovanillic and dihydroxyphenyl acetic acid levels in cerebrospinal fluid and extracts of brain tissue were determined after administration of ß-endorphin to animals pretreated or not with saloxone. The results suggest that ß-endorphin interferes with formation of dopaminergic metabolites by acting on opioid receptors