High-performance liquid chromatographic determination of phenylephrine and its conjugates in human plasma using solid-phase extraction and electrochemical detection.

An HPLC method for the determination of phenylephrine and its conjugates in human plasma was developed and validated. The method for quantitation involved extraction of diluted plasma (subject to hydrolysis with beta-glucuronidase for 30 min with 500 units of enzyme per 0.1 ml of plasma at 37 degrees C for the conjugates) on solid-phase weak cation-exchange cartridges followed by elution of the analyte and the internal standard (ethylnorphenylephrine) with 5% triethylamine in methanol.

Determination of m-hydroxymandelic acid, m-hydroxyphenylglycol and their conjugates in human plasma using liquid chromatography with electrochemical detection.

An LC method for the analysis of m-hydroxymandelic acid (MHMA) and m-hydroxyphenylglycol (MHPG) and their conjugates in human plasma was developed and validated. The method for the quantitation involved extraction of acidified plasma (subject to hydrolysis with beta-glucuronidase for 120 min with 500 units of enzyme/0.25 ml of plasma at 37 degrees C for the conjugates) with an organic phase (methyl-tert-butyl ether).

High-performance liquid chromatographic method for the determination of tris(hydroxymethyl)aminomethane (tromethamine) in human plasma.

Determination of tris(hydroxymethyl)aminomethane (tromethamine) in human plasma involved derivatization of the amino and hydroxyl groups with a ultraviolet-absorbing chromophore followed by extraction into an organic phase. Reversed-phase high-performance liquid chromatography with gradient elution was used for the separation of the analyte from the internal standard (2,3-butanediol). The assay was linear in the range 1.

Glucose-6-phosphate phosphohydrolase activity in guinea pig liver microsomes is influenced by phosphatidylcholine. Interaction with cholesterol-enriched membranes.

Guinea pig liver microsomal membranes were cholesterol-enriched by feeding guinea pigs a high-cholesterol diet. Cholesterol enrichment as well as partial lipid removal of normal native microsomes by acetone-butanol extraction resulted in 40-50% loss in activity of the glucose-6-phosphate phosphohydrolase (G-6-Pase) (EC 3.1.

Effect of cholesterol and temperature perturbations on membrane hydrolases and transport of calcium and glucose in guinea pig brush border membrane vesicles.

The function of membrane cholesterol (chol) in the regulation of membrane-bound hydrolases and transport proteins has been investigated in chol-enriched membranes of guinea pig intestinal brush borders. Chol-enrichment is accomplished by non-invasive means i.e.