ABSTRACT
A new synthetic procedure was used to prepare L-glutamyl-L-serine phosphate (Glu-Ser.P) with a good yield. The phosphopeptide is able to chelate calcium ion as shown by conductimetric titration and through the use of a calcium-specific electrode. Intestinal absorption of radioactive calcium is enhanced in rats fed 45Ca and Glu-Ser.P.
Subject(s)
Calcium/metabolism , Chelating Agents/chemistry , Dipeptides/chemistry , Phosphopeptides/chemistry , Administration, Oral , Animals , Calcium Radioisotopes/metabolism , Electric Conductivity , Intestinal Absorption/drug effects , RatsABSTRACT
Amino acids dissolved in aqueous methanol (or ethanol) and treated with optically active menthyl chloroformate were converted into N-menthyloxycarbonyl methyl (or ethyl) ester derivatives within a few minutes at room temperature. The obtained diastereomeric derivatives, with the exception of arginine and histidine, had suitable gas chromatographic properties allowing enantiomeric analysis of a large number of proteinogenic and synthetic amino acids.
Subject(s)
Amino Acids/chemistry , Formates , Alkylation , Chromatography, Gas , Esters , Molecular Structure , StereoisomerismABSTRACT
Serum levels of 7 alpha-hydroxycholesterol (7 alpha (OH)C) were found to increase considerably in hypercholesterolemic patients treated with cholestyramine. After 3-5 days, the normal level, which is in the range of 0.04 mg/l, rose to 1 mg/l. When the treatment was stopped it decreased rapidly with a half-life analogous to that of LDLs. This phenomenon was also observed in non-hypercholesterolemic humans. More than 75% of 7 alpha (OH)C is carried in blood by the LDLs.
Subject(s)
Cholestyramine Resin/therapeutic use , Hydroxycholesterols/blood , Hyperlipoproteinemia Type II/blood , Adolescent , Adult , Child , Child, Preschool , Cholestyramine Resin/administration & dosage , Humans , Hyperlipoproteinemia Type II/drug therapy , Kinetics , Lipoproteins, LDL/blood , Middle AgedABSTRACT
The intestinal absorption of 5,6 alpha-epoxy-5 alpha-cholesta-3 beta-ol, an oxysterol formed by cholesterol autoxidation, has been evaluated in the male Wistar rat. Measurement of the 14C/3H ratio in the serum (by the method of Zilversmit and Hugues) and in the feces showed that a large proportion of the epoxide was absorbed. Epoxide clearance from the blood was very rapid, but its excretion in the stool continued for several days, corresponding to the fraction of the epoxide stored in the animal.
Subject(s)
Cholesterol/analogs & derivatives , Intestinal Absorption , Animals , Carbon Radioisotopes , Cholesterol/metabolism , Feces/analysis , Kinetics , Male , Rats , Rats, Inbred Strains , TritiumABSTRACT
The products of cholesterol autoxidation (oxysterols) in heated animal food fat were determined qualitatively and quantitatively to evaluate their toxicity and those of the foods in which they occur. Samples of beef tallow were taken from deep-fat fryers while they were in use. The oxysterols were identified and assayed by gas liquid chromatography and thin layer chromatography on Chromarods with flame ionization detection (TLC-FID). The two methods were compared and the TLC-FID method was found more convenient for a rapid estimation of autoxidation. Of the original cholesterol, 25% was destroyed during cooking and partly transformed into 3 beta-5-6 beta-trihydroxy-5 alpha-cholestane, 7 alpha-hydroxy-, 7 beta-hydroxy-, 7-oxo-cholesterol, 7-oxo-cholesta-3-5-diene and cholesterol epoxides. Certain other oxysterols were present in smaller quantities.
Subject(s)
Cholesterol , Dietary Fats , Hot Temperature , Chromatography, Gas , Chromatography, Thin Layer , Cooking , Humans , Oxidation-Reduction , Sterols/analysisABSTRACT
Autoxidation of non-esterified cholesterol, in the solid state, at 100 degrees C, is known to be a relatively slow reaction. The presence of carefully chosen cholesteryl esters considerably increases the ratio of autoxidation. Using this method, mixtures of autoxidized free cholesterol (oxycholesterol) labelled on carbon 4 can be obtained almost quantitatively, in the presence of benzoyl peroxide. The ratio of [4-14C] ester produced by transesterification at the end of the reaction is about 10%.
