Picomole quantities of endogenous GABA in acidified superfusates of synaptosomal preparations have been measured using micro-bore ion-exchange chromatography and post-column formation of the fluorescent iso-indole derivative. Using this technique superfusates have been analyzed directly, without further manipulations, to investigate the release of endogenous GABA. Spontaneous release of GABA was 2–5 pmol/200 μl superfusate increasing to 20 pmol/200 μl with potassium stimulation. When γ-vinyl GABA (RMI 71754), an inhibitor of GABA-T was injected into rats (750 mg/kg) and synaptosomes prepared the potassium-evoked release of GABA was increased 3-fold compared to controls. Chromatographic separations and measurement of release of endogenous and radiolabeled GABA allowed the real specific activity of released GABA to be calculated. Only when 500 μM amino-oxyacetic acid was added during isolation of synaptosomes was the specific activity of released GABA the same as the initial specific activity.

A procedure is described for the measurement of DL-alpha-difluoromethylornithine (DFMO), a selective irreversible inhibitor of ornithine decarboxylase, in biological specimens. The drug is separated from other amino acids with a commerical amino-acid analyser and detected by formation of its alkylthio-isoindole derivative with o-phthalaldehyde. DFMO concentrations of 0.1 nmol can be determined in a sample volume of 100 microliter. The assay has been used to determine the half-life of DFMO in serum of several species and the relationships between serum and tissue concentrations.

1. 5-Hexyne-1,4-diamine (RMI 71696), an enzyme-activated irreversible inhibitor of ornithine decarboxylase (EC 4.1.1.17) in vitro, causes a rapid, long-lasting, dose-dependent decrease of ornithine decarboxylase activity in prostate and to a lesser extent in thymus and testis of rats when injected intraperitoneally. 2. 5-Hexyne-1,4-diamine activates S-adenosylmethionine decarboxylase (EC 4.1.1.50) in vitro, analogously to putrescine. 3. Three doses of 100 mg/kg 5-hexyne-1, 4-diamine given to rats during a 24 hr period markedly decrease putrescine concentrations in prostate, thymus and testis and spermidine concentrations in prostate.

The thin-layer electrophoretic separation at pH 4.8 of brain extracts and a procedure for fluorescent staining of the plates with fluorescamine are described for the rapid routine determination of 4-aminobutyric acid (GABA), glutamic acid and aspartic acid in brain extracts and in particulate fractions of brain tissue. Automated sample application, electrophoretic separation using two chambers, and quantitation by in situ fluorescence scanning allows the assay of 280 samples within three working days. The method is reproducible (S.D. <8% of the mean) within the range of 0.2–2 nmole per spot. The staining procedure can be applied to a variety of related analytical problems. The method has proved useful for the determination of the specific radioactivities of GABA, glutamic acid and aspartic acid in metabolic studies.

Euglene gracilis (strain Z) was found to contain five polyamines which could be separated by high-pressure cation-exchange chromatography. 1,3-Diaminopropane, putrescine, norspermidine (N-(3-aminopropyl)-1,3-diaminopropane), spermidine and norspermine (N,N'-bis(aminopropyl)-1,3-diaminopropane) were identified. Biosynthesis of putrescine in E. gracilis proceeds through decarboxylation of L-ornithine, no arginine decarboxylase (EC 4.1.1.19) activity could be detected. The properties of the enzymes ornithine decarboxylase (EC 4.1.1.17) and S-adenosylmethionine decarboxylase (EC 4.1.1.50) in this alga were found to be similar to those of the enzymes isolated from animal tissues or yeast cells. A bioxynthetic scheme is proposed which relates the different polyamines occurring in E. gracilis.

Procedures are described for the determination of methylpentynol carbamate in serum, either by injection into the chromatograph of diluted serum or extraction of the drug into chloroform and injection of an aliquot of the concentrated organic phase; a 4% CDMS column is used. Similar assays for measuring the metabolite 3-methylpentyne-3,4-diol in urine are reported. The methods have been used for measuring methylpentynol carbamate and its metabolite in samples from rats and dogs.