1. The metabolism of retinoic acid and retinyl acetate labelled with (14)C in various positions was studied after intravenous injection of physiological amounts of these compounds into retinol-deficient rats. 2. Analysis of the resultant radio-activity in the urine, carbon dioxide and faeces led to a postulation of the existence of three major pathways for the metabolism of these two compounds....

A "high-performance" liquid-chromatographic separation of retinoids (retinol, isotretinoin, all-trans retinoic acid, retinal, etretinate, and retinyl acetate) in serum is described. The separation was used in developing a quantitative assay for retinol (vitamin A) and two therapeutic analogs, isotretinoin (13-cis-retinoic acid) and etretinate (Ro 10-9359). The procedure requires 1 mL of serum. ...

A method is described for the simultaneous measurement of probucol, retinol, tocopherols, lycopene, and carotenes by reverse phase high performance liquid chromatography. A high sensitivity was achieved by use of a microbore column and by monitoring the effluent at the optimum wavelengths of each substance with a diode array detector. The detection limits were lycopene 0.5 ng; alpha-carotene, b...

BACKGROUND Golden Rice (GR) has been genetically engineered to be rich in β-carotene for use as a source of vitamin A. OBJECTIVE The objective was to compare the vitamin A value of β-carotene in GR and in spinach with that of pure β-carotene in oil when consumed by children. DESIGN Children (n = 68; age 6-8 y) were randomly assigned to consume GR or spinach (both grown in a nutrient solutio...

Isotope dilution is currently the most accurate technique in humans to determine vitamin A status and bioavailability/bioconversion of provitamin A carotenoids such as β-carotene. However, limits of MS detection, coupled with extensive isolation procedures, have hindered investigations of physiologically-relevant doses of stable isotopes in large intervention trials. Here, a sensitive liquid ch...

The vitamin A (VA) value of carotenoids from fruits and vegetables is affected by many factors. This study determined the VA value of -carotene isolated from carrots compared with -carotene and retinyl acetate supplements fed to Mongolian gerbils (Meriones unguiculatus). Gerbils (n 38) were fed a VA-free diet for 4 wk. At baseline, 6 gerbils were killed to determine liver VA. Gerbils were divid...

1. retro-Retinyl acetate was shown to exert its biological activity by conversion into vitamin A. 2. When administered orally, retro-retinyl acetate was hydrolysed to retro-retinol in the intestine, isomerized to retinol and esterified before being transported to the liver for storage. 3. Administration of the compound at as high a dose as 4.0mg./day for 4 days led to the accumulation of both v...

Effect of vitamin A compounds on the covalent binding of benzo(a)pyrene [B(a)P] to subnuclear components was studied using rat liver nuclei in vitro. The retinol-induced inhibition of the covalent binding of B(a)P depended both on the dose and the time of addition. Retinal and retinyl acetate were both potent inhibitors, but retinoic acid was less effective. Retinol induced marked inhibition of...