Simple HPLC-EC Method for the Simultaneous Determination of Biogenic Amines and Their Main Metabolites in Small Rat Brain Regions

Peripheral serotonin dynamics in the rainbow trout (Oncorhynchus mykiss)

Serotonin (5-hydroxytryptamine, 5-HT) occurs in a wide range of tissues throughout the body of the rainbow trout. Results reported here indicate that the main peripheral sources of serotonin are the intestinal tract and the gill epithelium (levels above 1500 ng/g). The high intestinal serotonin concentration is mostly due to serotoninergic nerve fibres, which are present at high density in the intestinal wall. Only about 2% of serotonin is associated with mucosal enterochromaffin cells. In the remaining tissues studied serotonin concentration was below 160 ng/g: the highest concentrations were seen in the anterior and posterior kidneys, followed by the liver, heart, and spleen. 5-Hydroxyindolacetic acid (5-HIAA) levels, except in plasma, were generally lower than serotonin levels, and were below our detection limits in heart, spleen and posterior kidney. Acute d-fenfluramine treatment (5 or 15 mg/kg i.p.) significantly increased 5-HIAA/5-HT ratio in the anterior intestine, pyloric caeca and plasma. Serotonin released from intestinal serotoninergic fibres in response to d-fenfluramine treatment is metabolized locally, and only a small part reaches the blood, from where it can be taken up and metabolized by other peripheral tissues, such as the liver and gill epithelium. The non-metabolized serotonin pool in the blood appears to be located extracellularly, not intracellularly as in mammals. In view of these findings, we present an overview of peripheral serotonin dynamics in rainbow trout.

Rapid determination of tyramine in fish feed and slaughter offal by HPLC using coulometric detection

Fish feed and slaughter offal products may contain decomposition compounds such as biogenic amines. Owing to their harmful effects on animals fed with such products, there is a need for determining the amine content. In the work a simple and fast HPLC method, based on coulometric detection (EC) measuring only tyramine, was developed for routine quality screening. The samples were extracted with 0.4 mol/L perchloric acid and analysed directly by HPLC using a mobile phase of 0.2 mol/L potassium dihydrogen phosphate in water at pH 3. Tyramine was detected using a coulometric detector consisting of two analytical cells, the first one at 0.4 V and the second at 0.7 V. The calibration was linear over the range 4.52 to 452 ng/ml. The minimum detectable quantity was 10 pg/20 microliters. The reproducibility and the recoveries were high. Comparison of the tyramine content measured by EC or derivatization followed by ultraviolet detection showed that both methods gave similar results. HPLC using EC is a fast and sensitive method for analysing tyramine reliably in fish feed and slaughter offal samples without any time-consuming derivatization steps.

Determination of urinary 5-hydroxy-3-indoleacetic acid by an automated HPLC method

A HPLC method for the quantitative determination of 5-hydroxy-3-indoleacetic acid (5-HIAA) in urine is described. The method is based on ion-pair chromatography, reversed phase (RP) column material and specific fluorimetric detection at 300 nm and 355 nm. Sample preparation and gradient elution were avoided by using a column-switching technique. The sensitivity of the assay was excellent for clinical routine analysis, with a detection limit of 0.2 mg/L 5-HIAA. No endogenous or exogenous interference problems arose. Intra- and interassay precision was good, with observed coefficients of variation of 1.5 to 2.6% and 2.1%, respectively. Recoveries were 93 to 98%. The system described can be used for clinical diagnosis and therapy follow-up of carcinoid tumors. It has been running for over a year without disturbances and with a minimum of technical attendance.

Opposing actions of D-1 and D-2 dopamine receptor-mediated alterations of adenosine-3',5'-cyclic monophosphate (cyclic AMP) formation during the amphetamine-induced release of endogenous dopamine in vitro

Changes in the formation of cyclic AMP following d-amphetamine (0.1 to 20 mumol/l) were examined in vitro in striatal slices of the rat. d-Amphetamine caused a dose-related increase in cyclic AMP content. This action of d-amphetamine was abolished by tissue pretreatment with reserpine (2.5 mg/kg, i.p.) and 3-iodotyrosine (1 mmol/l). By contrast, both clorgyline (0.1 mumol/l) and nomifensine (30 mumol/l) enhanced the d-amphetamine-induced increase in cyclic AMP formation. In superfusion experiments, a strong correlation between endogenous dopamine and cyclic AMP release was observed before, during and after d-amphetamine exposure. Finally, Sch 23390 (10 mumol/l) abolished while (-)sulpiride (10 mumol/l) enhanced the amphetamine-induced increase in cyclic AMP content. These results suggest that d-amphetamine enhances the formation of cyclic AMP through the release of endogenous dopamine into the synapse where it can interact with both D-1 and D-2 dopamine receptors. These results provide direct evidence that the antagonistic properties of D-1 and D-2 receptors on cyclic AMP formation are apparent at striatal synapses during release of endogenous neuronal dopamine.