These studies report the hydrolysis of retinyl palmitate with liver homogenates and homogenate fractions from retinol-depleted rats. The studies utilized an effective in vitro assay for retinyl palmitate hydrolase (RPH) activity, in which microgram amounts of retinyl palmitate were employed as substrate, followed by the chromatographic separation and fluorescence assay of free and esterified re...

We assessed the effects of prolonged reduction of plasma retinol concentrations (hyporetinolemia) on the distribution of tissue vitamin A (VA) and of its active compounds using a model of continuous recombinant human interleukin-6 (rhIL-6) infusion via osmotic minipumps in VA-sufficient male rats. Plasma retinol and retinol-binding protein (RBP) concentrations remained decreased and lower in rh...

Retinol (vitamin A alcohol) is an accepted adjunctive treatment in infections such as measles. There is also indirect evidence from in vitro, animal and human studies that retinol supplementation may be beneficial in severe malaria. There have, however, been no studies that have examined the pharmacokinetics of acute retinol supplementation in severe illness. To establish whether mobilization o...

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...

OBJECTIVE To investigate the effect of vitamin A supplementation on the retinol concentration in colostrum under fasting and postprandial conditions. METHODS This was a quasi-experimental study, with before and after assessments, conducted with 33 patients treated at a public maternity hospital. Blood and colostrum samples were collected under fasting conditions in the immediate postpartum pe...

Esterification of all-trans-retinol is a key reaction of the vertebrate visual cycle, since it produces an insoluble, relatively non-toxic, form of the vitamin for storage and supplies substrate for the isomerization reaction. CoA-dependent and -independent pathways have been described for retinol esterification in retinal pigment epithelium (RPE). The CoA-independent reaction, catalysed by lec...

BACKGROUND The relative dose response (RDR) test, which quantifies the increase in serum retinol after vitamin A administration, is a qualitative measure of liver vitamin A stores. Particularly in preterm infants, the feasibility of the RDR test involving blood is critically dependent on small sample volumes. OBJECTIVES This study aimed to assess whether the RDR calculated with retinol-bindin...

The retinal pigment epithelium (RPE) is responsible for transport of retinol from the choroidal circulation to the photoreceptors. In the intact eye, this process is mediated by membrane receptors for plasma retinol binding protein (RBP) distributed basolaterally on the RPE cells. We have shown that cultured human RPE expresses this receptor. A binding curve exhibiting saturation was generated ...

INTRODUCTION Retinols seem to be of clinical importance in ameliorating the clinical consequences of septic shock. These beneficial effects of retinols are suggested to be due to an antioxidant property. The present study was undertaken in order to confirm or rule out such an effect of retinol palmitate (RP) in experimental septic shock by measuring F2-isoprostanes and a major prostaglandin F2 ...