Methods were developed for the analysis of 5-hydroxytryptamine, related indolealkylamines (tryptamine, melatonin, 5-methoxytryptamine, N-acetyl-5-hydroxytryptamine and 6-hydroxymelatonin) and 5-hydroxyindole-3-acetic acid (5HIAA) in bovine retina, aqueous and vitreous humours. 5-Hydroxytryptamine and related indolealkylamines were extracted and derivatized to form their corresponding pentafluoropropionyl spirocyclic derivatives. 5HIAA was extracted and derivatized to the corresponding pentafluoropropionamide-trifluoroethyl derivative. Identification and quantitation by gas chromatography-negative ion chemical ionization mass spectrometry was made with reference to deuteriated internal standards. 5-Hydroxytryptamine was present in all (n = 34) retinal samples analysed (20.53 +/- 1.64 ng) while N-acetyl-5-hydroxytryptamine was detected in half of the samples of retina (0.06 +/- 0.02 ng). Melatonin (0.15 +/- 0.06 ng) and tryptamine (0.78 +/- 0.34 ng) were detected in only a small number of retinas. 5-Methoxytryptamine was not present in retina. 5-Hydroxytryptamine was also present in aqueous (0.76 +/- 0.17 ng ml-1 and vitreous (0.35 +/- 0.05 ng ml-1' humours from bovine eye. Tryptamine, melatonin, 5-methoxytryptamine and N-acetyl-5-hydroxytryptamine were not detected in bovine aqueous and vitreous humours. 5HIAA was found in both bovine aqueous (2.03 +/- 0.38 ng ml-1) and vitreous (0.65 +/- 0.06 ng ml-1) humours, but its consistent determination in retina was obviated by interference from spurious peaks.

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Measurement of ascorbic acid in human aqueous humour and plasma and bovine aqueous humour by high-performance liquid chromatography with electrochemical detection.

High-performance liquid chromatography (HPLC) on ODS silica with cetyltrimethylammonium bromide as an ion-pairing reagent and electrochemical detection (ECD) was used to determine ascorbic acid in bovine and human aqueous humour and human plasma. Hydroquinone was used as the internal standard. A calibration curve plotted with ascorbic acid concentrations in the range 0.5-5 micrograms ml-1 for peak height versus internal standard peak height had a correlation coefficient of 0.998. The RSD (precision) between analyses of the same diluted sample was 1.5% and the RSD (reproducibility) between analyses of separate aliquots of the same sample of aqueous humour was 1.6%.

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The metabolism of fluorometholone by bovine cornea.

Isolated bovine cornea was found to reduce the 20 ketone group in fluorometholone (FML) to produce a mixture of 20 alpha- and 20 beta-dihydrofluorometholone (DHFML). Incubation of FML with bovine cornea at pH 7.4 in phosphate buffer produced an increase in the amount of reduction products up to 8 h; after this time the rate of reduction decreased. The reduced products were quantified by GC-MS against [2H3] 20 alpha-DHFML. Variable amounts of 20 beta-DHFML were detected in six samples of human aqueous humour following topical application of 50 micrograms of FML to the eye. The rapid metabolism of the side chain of FML may account for the unexpected low concentrations of FML which are found in human aqueous humour following its application to the surface of the eye.

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PubMedDate not supplied

The determination of biogenic amines in four strains of the fruit fly Drosophila melanogaster.

A range of biogenic amines were measured in the heads from four strains of Drosophila melanogaster. Quantitation was carried out using gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) with stable isotope dilution. The principal amines detected in the heads were dopamine, noradrenaline and 5 HT with small amounts of p- and m-tyramine; p-octopamine could not be detected in samples of 25 heads with a limit of detection of 10 pg per sample. In addition to conventional neurotransmitters or putative neurotransmitters the amines 5- and 6-hydroxydopamine were detected in the heads in substantial amounts.

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PubMedDate not supplied

Stereochemical origin of some clinically significant drug safety concerns: lessons for future drug development.

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