To assess the effect of zinc supplementation on plasma retinol levels, 24 preterm infants were randomly assigned to receive 400 micrograms.kg-1.d-1 of intravenous Zn or no Zn supplementation. Intakes of protein, energy, and vitamin A were similar for both groups as were day 0 plasma concentrations of retinol, retinol-binding protein (RBP), and Zn. Zn concentrations were not significantly differ...

Vitamin A (retinol) is a fat-soluble alcohol and is derived in the upper part of the small intestine from carotenoid plant pigments and Vitamin A esters present in food (Olson, I964). The free retinol then penetrates through the mucosal cells, perhaps aided by its polar or hydrophilic hydroxy group, and is re-esterified during transit (Glover and Walker, I 964). After absorption it reaches the ...

A compartmental model was developed to describe the metabolism of vitamin A in rats with low vitamin A status maintained by a low dietary intake of vitamin A (approximately 2 micrograms retinol equivalents/day). After the IV bolus injection of [3H]retinol in its physiological transport complex, tracer and trace data were obtained from plasma, organs (liver, kidneys, small intestine, eyes, adren...

[3H]Retinoic acid (RA) and [3H]retinol bind in an unsaturable manner to isolated nuclei from Nulli-SCC1 and PCC4.aza1R embryonal carcinoma (EC) cells. When nuclei are challenged with the same labeled retinoids on their respective binding proteins (CRABP and CRBP), much less binding is observed and the binding is saturable. RA-CRABP does not compete with [3H]retinol-CRBP for binding to specific ...

The interaction of human plasma retinol-binding protein with plasma prealbumin was studied by the techniques of velocity ultracentrifugation and polarization of retinol fluorescence. In the first method the unbound fraction of retinol-binding protein, which sediments more slowly than its complexes with prealbumin, was measured by its absorption. A stoichiometry of retinol-binding protein to pre...

Vitamin A (retinol) plays a key role in the regulation of cell growth and differentiation, and has been studied as a potential chemopreventive agent for prostate cancer. However, findings from epidemiologic studies on the association between circulating retinol concentrations and the risk of prostate cancer are inconsistent. We examined whether serum concentrations of retinol were associated wi...

Iron deficiency seems to deteriorate vitamin A metabolism leading to a reduction in serum retinol and an increase in hepatic retinol and retinyl ester. These alterations probably result from an increase in retinol sequestration to the liver and/or impairment in the activity of hepatic retinyl ester hydrolases decreasing vitamin A mobilization.

Background: Vitamin A (VA; retinol) supplementation is widely used to reduce child mortality in low-income countries. However, existing research suggests that supplementation with VA alone may not be optimal for infants. Objective: We compared the effect of VA with VA combined with retinoic acid (VARA) on retinol uptake and turnover in organs of neonatal rats raised under VA-marginal conditions...

Hepatocytes and hepatic stellate cells play important roles in retinoid storage and metabolism. Hepatocytes process postprandial retinyl esters and are responsible for secretion of retinol bound to retinol-binding protein (RBP) to maintain plasma retinol levels. Stellate cells are the body's major cellular storage sites for retinoid. We have characterized and utilized an immortalized rat stella...