Rapid measurement of the monoamine content in small volumes of rat plasma

Skin tissue sample collection, sample homogenization, and analyte extraction strategies for liquid chromatographic mass spectrometry quantification of pharmaceutical compounds

Quantification of pharmaceutical compounds in skin tissue is challenging because of low expected concentrations, small typical sample volumes, and the hard nature of the skin structure itself. This review provides a comprehensive overview of sample collection, sample homogenization and analyte extraction methods that have been used to quantify pharmaceutical compounds in skin tissue, obtained from animals and humans, using liquid chromatography-mass spectrometry. For each step in the process of sample collection to sample extraction, methods are compared to discuss challenges and provide practical guidance. Furthermore, liquid chromatographic-mass spectrometry considerations regarding the quality and complexity of skin tissue sample measurements are discussed, with emphasis on analyte recovery and matrix effects. Given that the true recovery of analytes from skin tissue is difficult to assess, the extent of homogenization plays a crucial role in the accuracy of quantification. Chemical or enzymatic solubilization of skin tissue samples would therefore be preferable as homogenization method.

The protective effects of resveratrol on social stress-induced cytokine release and depressive-like behavior

Social stress is a risk factor for psychiatric disorders, however only a subset of the population is susceptible while others remain resilient. Inflammation has been linked to the pathogenesis of psychosocial disorders in humans and may underlie these individual differences. Using a resident-intruder paradigm capable of revealing individual differences in coping behavior and inflammatory responses, the present study determined if resveratrol (RSV; 0, 10, 30mg/kg/day) protected against persistent stress-induced inflammation in socially defeated rats. Furthermore, the antidepressant efficacy of RSV was evaluated using the sucrose preference test. Active coping rats were characterized by more time spent in upright postures and increased defeat latencies versus passive coping rats. Five days after defeat, flow cytometry revealed enhanced stimulation of proinflammatory proteins (IL-β, TNF-α) in spleen cells of passive rats as compared to active coping and controls, an effect that was blocked by both doses of RSV. Furthermore, only passive coping rats exhibited increased proinflammatory proteins (IL-1β, TNF-α, GM-CSF) in the locus coeruleus (LC), a noradrenergic brain region implicated in depression. Notably, only 30mg/kg RSV blocked LC neuroinflammation and importantly, was the only dose that blocked anhedonia. Alternatively, while stress had minimal impact on resting cytokines in the dorsal raphe (DR), RSV dose-dependently reduced DR cytokine expression. However, this did not result in changes in indoleamine 2,3-dioxygenase activity or serotonin levels. Taken together, these data suggest that social stress-induced depressive-like behavior evident in passive coping rats may be driven by stress-induced neuroinflammation and highlight natural anti-inflammatory agents to protect against social stress-related consequences.

Forced swimming stress does not affect monoamine levels and neurodegeneration in rats

OBJECTIVE

The current study was aimed to investigate the correlations between immobility time in the forced swimming test (FST, a behavioral indicator of stress level) and hippocampal monoamine levels (markers of depression), plasma adrenalin level (a peripheral marker of stress) as well as fluoro-jade C staining (a marker of neurodegeneration).

METHODS

Male Sprague-Dawley rats were subjected to acute, sub-chronic (7 d) or chronic (14 d) FSTs and immobility time was recorded. Levels of noradrenalin, serotonin and dopamine in the hippocampus, and adrenalin level in the plasma were quantified by high-performance liquid chromatography with electrochemical detection. Brain sections from rats after chronic forced swimming or rotenone treatment (3 mg/kg subcutaneously for 4 d) were stained with fluoro-jade C.

RESULTS

The rats subjected to swimming stress (acute, sub-chronic and chronic) showed long immobility times [(214 +/- 5), (220 +/- 4) and (231 +/- 7) s, respectively], indicating that the animals were under stress. However, the rats did not exhibit significant declines in hippocampal monoamine levels, and the plasma adrenalin level was not significantly increased compared to that in unstressed rats. The rats that underwent chronic swimming stress did not manifest fluoro-jade C staining in brain sections, while degenerating neurons were evident after rotenone treatment.

CONCLUSION

The immobility time in the FST does not correlate with markers of depression (monoamine levels) and internal stress (adrenalin levels and neurodegeneration), hence this parameter may not be a true indicator of stress level.

Catecholamine levels and receptor expression in low protein rat offspring

AIMS

Low birthweight in humans has been shown to lead to increased resting pulse rate in adult life, suggesting possible increased sympathoadrenal activity. The hypothesis that early growth restriction is associated with permanent alterations in catecholamine metabolism was tested.

METHODS

Circulating catecholamine concentrations (by radioimmunoassay) and adipocyte adrenoceptor expression from different fat depots (by Western blot) were estimated in 12-week-old male offspring of rat dams fed a reduced protein diet during pregnancy and lactation.

RESULTS

In the fed state, median (interquartile range) plasma adrenaline concentrations for male control and low protein offspring rats were: 0.65 (0.48-0.86) vs. 1.42 (0.89-1.87) nmol/l (P < 0.005), respectively. Equivalent noradrenaline concentrations were: 2.71 (2.16-3.46) vs. 3.45 (3.00-4.28) nmol/l (P < 0.05). After 24 h starvation, plasma adrenaline concentrations of controls rose to become similar to those of low protein offspring: 1.03 (0.95-1.31) vs. 1.41 (0.69-1.62) nmol/l (P = 0.3), respectively. Noradrenaline concentrations rose in both groups to become similar: 3.84 (3.33-4.54) vs. 4.32 (3.70-6.54) nmol/l (P = 0.3). In epididymal adipocytes adrenoceptor expression (relative to that of controls) was: alpha2A 0.79 (0.66-0.94) (P = 0.08), beta1 2.60 (2.27-3.07) (P = 0.04), beta3 1.37 (1.27-1.46) (P = 0.02). Similar-pattern differences in adrenoceptor expression were observed in subcutaneous and intra-abdominal adipocytes.

CONCLUSIONS

These results are consistent with the suggestion that long-term alterations in catecholamine metabolism are present in adult offspring of rats fed a reduced protein diet during pregnancy and lactation.

Effective capillary electrophoresis-based heteroduplex analysis through optimization of surface coating and polymer networks

The efficacy of capillary electrophoresis for detecting DNA mutations via heteroduplex analysis (HDA) is dependent upon both the effective passivition of the capillary surface and the choice of the correct polymer network for sieving. Using HDA with laser-induced fluorescence detection of fluorescently labeled DNA fragments, an effective coating and optimal polymer matrix were sought. Optimized separation conditions were determined through the methodological evaluation of a number of different silanizing reagents, polymeric coatings, and polymer networks for resolving the PCR-amplified DNA fragments associated with five mutations (185delAG, 1294del40, 4446C > G, 5382insC, 5677insA) in the breast cancer susceptibility gene (BRCA1). For capillary coating, allyldimethylchlorosilane, 4-chlorobutyldimethylchlorosilane, (gamma-methacryloxypropyl)trimethoxysilane, chlorodimethyloctylsilane (OCT), and 7-octenyltrimethoxysilane were evaluated as silanizing reagents in combination with poly(vinylprrolidone) (PVP) and polyacrylamide (PA) as the polymeric coat. The HDA results were compared with those obtained using a commercial (FC) coated capillary. Of these, the OCT-PVP combination was found to be most effective. Using this modified capillary, HDA with polymer networks that included hydroxyethylcellulose (HEC), linear polyacrylamide, and PVP showed that a PVP-, PA-, or FC-coated capillary, in combination with HEC as the sieving polymer, could be used effectively to discriminate the mutations in less than 10 min. However, optimal performance was observed with the OCT-PVP-coated capillary and HEC as the polymer network.

Determination of erythromycin in urine and plasma using microbore liquid chromatography with tris(2,2'-bipyridyl)ruthenium(II) electrogenerated chemiluminescence detection

Erythromycin is determined in both urine and plasma samples using microbore reversed-phase liquid chromatography with tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)3(2+)] electrogenerated chemiluminescence (ECL) detection. Ru(bpy)3(2+) is included in the mobile phase thus eliminating band broadening caused by post-column reagent addition. Extra column band broadening is an important concern in microbore liquid chromatography due to the small peak volumes. Erythromycin was studied in both water and biological samples. The detection limit for erythromycin in standards is 0.01 microM or 50 fmol injected with a S/N of 3 and a linear working range that extends four orders of magnitude. Human urine and blood plasma were also studied. Urine samples were diluted and filtered before injection. Ultrafiltration was used to remove protein from blood plasma samples prior to injection. Erythromycin was selectively detected in the body fluid samples without any further sample preparation. The detection limits obtained for erythromycin in urine and plasma are 0.05 and 0.1 microM, respectively, for 5 microl injected on a 150x1 mm I.D. C18 column.

Aspirin inhibits collagen-induced platelet serotonin release, as measured by microbore high-performance liquid chromatography with electrochemical detection

A sensitive microbore high-performance liquid chromatographic method with electrochemical detection has been developed for the measurement of small quantities of serotonin (5-hydroxytryptamine; 5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in rabbit platelets. The limit of detection of 5-HT is 0.1 ng/ml. To evaluate the 5-HT release from platelet suspension, the aggregating agent collagen was added at concentrations of 10, 30 and 100 micrograms/ml and the 5-HT concentrations rose from the base level (11.80 +/- 0.42 ng/ml) to 123.97 +/- 11.02, 361.96 +/- 17.90 and 470.45 +/- 35.46 ng/ml, respectively. Further results demonstrated that aspirin inhibits collagen-induced 5-HT release from platelet suspension significantly.