scholarly journals Serum and intracellular retinol transport in the equine

1982 ◽  
Vol 47 (2) ◽  
pp. 273-280 ◽  
Author(s):  
D. Sklan ◽  
Susan Donoghue
Keyword(s):  
Vitamin A ◽  
Gel Filtration ◽  
Protein Aggregates ◽  
Retinyl Palmitate ◽  
Hydrolase Activity ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Protein Aggregate ◽  
Retinyl Esters ◽  
Four Levels

1. Serum and intracellular distribution of retinol was determined in equines maintained on four levels of vitamin A intake.2. The form of retinol transported in serum was determined by gel filtration and chromatography to be a complex of retinol bound to a protein of molecular weight (MW) of approximately 20000, which was in turn complexed probably with prealbumin to yield a complex with a MW of 75000 to 80000.3. Increasing dietary vitamin A levels enhanced the concentration of lipoprotein-bound retinyl esters in the plasma.4. Vitamin A in the liver cytosol was found predominantly as retinyl esters in a lipid–protein aggregate of MW approximately 2 × 106 and hydrated density of 1·063–1·111. In the kidney and adrenal gland, two Iipid–protein entitites were found with MW of approximately 1·8 × 106 and 1·7 × 105 respectively. These fractions contained approximately 40 and 20% lipid respectively and had densities of 1·063–1·111 and approximately 1·21.5. All lipid–protein aggregates were associated with retinyl palmitate hydrolase activity and guanidine treatment released a 15000 MW material, presumably intracellular retinol-binding protein.6. Increasing dietary vitamin A enhanced the proportion of retinol in the 1·7 × 105 fraction.7. Findings in equine plasma and liver resemble previous observations in other species. The characterization of two new lipid–protein aggregates in equine kidney and adrenal glands, which have hydrolase activity, may be important in intracellular retinol transport and metabolism, especially in animals subjected to high intakes of vitamin A.

scholarly journals Vitamin A Transporters in Visual Function: A Mini Review on Membrane Receptors for Dietary Vitamin A Uptake, Storage, and Transport to the Eye

Nutrients ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 3987
Author(s):  
Nicasio Martin Ask ◽  
Matthias Leung ◽  
Rakesh Radhakrishnan ◽  
Glenn P. Lobo
Keyword(s):  
Cell Growth ◽  
Vitamin A ◽  
Visual Function ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Peripheral Tissues ◽  
Retinol Binding Protein 4 ◽  
Retinyl Esters ◽  
And Function

Vitamins are essential compounds obtained through diet that are necessary for normal development and function in an organism. One of the most important vitamins for human physiology is vitamin A, a group of retinoid compounds and carotenoids, which generally function as a mediator for cell growth, differentiation, immunity, and embryonic development, as well as serving as a key component in the phototransduction cycle in the vertebrate retina. For humans, vitamin A is obtained through the diet, where provitamin A carotenoids such as β-carotene from plants or preformed vitamin A such as retinyl esters from animal sources are absorbed into the body via the small intestine and converted into all-trans retinol within the intestinal enterocytes. Specifically, once absorbed, carotenoids are cleaved by carotenoid cleavage oxygenases (CCOs), such as Beta-carotene 15,15’-monooxygenase (BCO1), to produce all-trans retinal that subsequently gets converted into all-trans retinol. CRBP2 bound retinol is then converted into retinyl esters (REs) by the enzyme lecithin retinol acyltransferase (LRAT) in the endoplasmic reticulum, which is then packaged into chylomicrons and sent into the bloodstream for storage in hepatic stellate cells in the liver or for functional use in peripheral tissues such as the retina. All-trans retinol also travels through the bloodstream bound to retinol binding protein 4 (RBP4), where it enters cells with the assistance of the transmembrane transporters, stimulated by retinoic acid 6 (STRA6) in peripheral tissues or retinol binding protein 4 receptor 2 (RBPR2) in systemic tissues (e.g., in the retina and the liver, respectively). Much is known about the intake, metabolism, storage, and function of vitamin A compounds, especially with regard to its impact on eye development and visual function in the retinoid cycle. However, there is much to learn about the role of vitamin A as a transcription factor in development and cell growth, as well as how peripheral cells signal hepatocytes to secrete all-trans retinol into the blood for peripheral cell use. This article aims to review literature regarding the major known pathways of vitamin A intake from dietary sources into hepatocytes, vitamin A excretion by hepatocytes, as well as vitamin A usage within the retinoid cycle in the RPE and retina to provide insight on future directions of novel membrane transporters for vitamin A in retinal cell physiology and visual function.

Vitamin A in Blood Plasma and Urine of Dogs is Affected by the Dietary Level of Vitamin A

2000 ◽  
Vol 70 (3) ◽  
pp. 84-91 ◽  
Author(s):  
Florian Schweigert ◽  
Volker Bok
Keyword(s):  
Vitamin A ◽  
Blood Plasma ◽  
Plasma Levels ◽  
Current Knowledge ◽  
Retinyl Palmitate ◽  
Dietary Vitamin ◽  
Urinary Levels ◽  
Retinyl Esters ◽  
Prolonged Feeding ◽  
In Blood Plasma

Dogs differ from other species with respect to the occurrence of a high percentage of retinyl esters in blood plasma and the excretion of substantial amounts of vitamin A in the urine. Our investigation focussed on the effects of different concentrations of vitamin A in the diet, ranging from concentrations below NRC requirements of 25 IU/kg body weight (BW) to 2400 IU/kg BW, on the levels of retinol and retinyl esters (palmitate/oleate and stearate) in canine blood plasma and urine. The plasma levels of retinyl esters paralleled the levels of vitamin A in the feed (r = 0.91; p < 0.001). The highest plasma level (12.1 ± 0.4 mg/l) was observed at the highest level in the diet. This observation may be explained by the fact that in dogs retinyl esters are associated with lipoproteins. Even under prolonged feeding on vitamin A levels below NRC requirements, retinyl esters were still present in the plasma (2.8 ± 0.1 mg/l). Levels of retinol were not affected (1.2 ± 0.03 vs. 1.0 ± 0.03 mg/l, respectively). In the urine, the concentration of retinol and retinyl palmitate/oleate increased with the first increase of vitamin A in the diet to 1.2 ± 0.4 mg/l of total vitamin A. Urinary levels were elevated and fluctuated with up to four peaks while dietary vitamin A levels were above NRC requirements. But the amount of retinol and retinyl esters excreted did not show any dependence on the amount of vitamin A in the diet. When the amount of vitamin A in the diet was at or below requirements, only traces of retinol and retinyl esters were detected in urine. Thus, contrary to current knowledge for most other mammals, retinyl ester levels in plasma and retinol and retinyl esters in the urine of dogs proved to be clearly but differently affected by the amount of vitamin A supplied with the diet. Contrary to retinol, plasma levels of retinyl esters closely reflect the actual supply of vitamin A with the feed. The occurrence of retinol and retinyl esters in urine may, however, be due to dietary supply of vitamin A in excess of standard requirements, thereby providing a useful indicator of a dietary supply of vitamin A above requirement. The mechanism involved in the possible regulation of urinary excretion of retinol and retinyl esters remains to be elucidated.

scholarly journals Opposing actions of cellular retinol-binding protein and alcohol dehydrogenase control the balance between retinol storage and degradation

2004 ◽  
Vol 383 (2) ◽  
pp. 295-302 ◽  
Author(s):  
Andrei MOLOTKOV ◽  
Norbert B. GHYSELINCK ◽  
Pierre CHAMBON ◽  
Gregg DUESTER
Keyword(s):  
Retinoic Acid ◽  
Vitamin A ◽  
Alcohol Dehydrogenase ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Gene Encoding ◽  
Retinyl Ester ◽  
Ester Formation ◽  
Retinyl Esters ◽  
Cellular Retinol Binding Protein

Vitamin A homoeostasis requires the gene encoding cellular retinol-binding protein-1 (Crbp1) which stimulates conversion of retinol into retinyl esters that serve as a storage form of vitamin A. The gene encoding alcohol dehydrogenase-1 (Adh1) greatly facilitates degradative metabolism of excess retinol into retinoic acid to protect against toxic effects of high dietary vitamin A. Crbp1−/−/Adh1−/− double mutant mice were generated to explore whether the stimulatory effect of CRBP1 on retinyl ester formation is due to limitation of retinol oxidation by ADH1, and whether ADH1 limits retinyl ester formation by opposing CRBP1. Compared with wild-type mice, liver retinyl ester levels were greatly reduced in Crbp1−/− mice, but Adh1−/− mice exhibited a significant increase in liver retinyl esters. Importantly, relatively normal liver retinyl ester levels were restored in Crbp1−/−/Adh1−/− mice. During vitamin A deficiency, the additional loss of Adh1 completely prevented the excessive loss of liver retinyl esters observed in Crbp1−/− mice for the first 5 weeks of deficiency and greatly minimized this loss for up to 13 weeks. Crbp1−/− mice also exhibited increased metabolism of a dose of retinol into retinoic acid, and this increased metabolism was not observed in Crbp1−/−/Adh1−/− mice. Our findings suggest that opposing actions of CRBP1 and ADH1 enable a large fraction of liver retinol to remain esterified due to CRBP1 action, while continuously allowing some retinol to be oxidized to retinoic acid by ADH1 for degradative retinoid turnover under any dietary vitamin A conditions.

Dietary Vitamin A and Visceral Adiposity: A Modulating Role of the Retinol-Binding Protein 4 Gene

2015 ◽  
Vol 8 (4-6) ◽  
pp. 164-173 ◽  
Author(s):  
Katie Goodwin ◽  
Michal Abrahamowicz ◽  
Gabriel Leonard ◽  
Michel Perron ◽  
Louis Richer ◽  
...  
Keyword(s):  
Vitamin A ◽  
Binding Protein ◽  
Visceral Adiposity ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Retinol Binding Protein 4

Simultaneous determination of retinol and retinyl esters in serum or plasma by reversed-phase high-performance liquid chromatography.

1978 ◽  
Vol 24 (11) ◽  
pp. 1920-1923 ◽  
Author(s):  
M G DeRuyter ◽  
A P De Leenheer
Keyword(s):  
Vitamin A ◽  
High Performance ◽  
Chromatographic Determination ◽  
Reversed Phase ◽  
Retinyl Palmitate ◽  
Serum Retinol ◽  
Liquid Chromatographic Determination ◽  
Retinyl Esters ◽  
Liquid Chromatographic

Abstract We propose a single-run liquid-chromatographic determination, with ultraviolet detection at 330 nm, for serum retinol and retinyl esters. The vitamin A derivatives are extracted according to the Bligh-Dyer procedure. With 200 microliter or serum, the lower detection limit is 50 microgram/liter for retinol and about 100 microgram/liter for retinyl esters. Within-run precision (CV) was 2.3% for retinol, 4.3% for retinyl palmitate. Day-to-day percision (CV, n = 20) for retinol was 4.9% during a month. The method can be used for the assessment of vitamin A absorption tests and for the determination of serum retinol (normal, subnormal, and above-normal concentrations). Serum retinyl esters can only be measured in conditions where concentrations exceed 100 microgram/liter.

Effect of dietary vitamin A on the mixed function oxidases and the pneumotoxicity of 3-methylindole in goats

1983 ◽  
Vol 61 (8) ◽  
pp. 816-821 ◽  
Author(s):  
F. E. Burley ◽  
T. M. Bray
Keyword(s):  
Vitamin A ◽  
Clinical Signs ◽  
Weight Ratio ◽  
Dry Weight ◽  
Retinyl Palmitate ◽  
Lung Damage ◽  
Dietary Vitamin ◽  
Vitamin A Supplementation ◽  
High Vitamin ◽  
Alveolar Epithelial

To determine the effects of dietary vitamin A on the activity of the mixed function oxidase (MFO) system and on the susceptibility to 3-methylindole (3MI)-induced respiratory disease, goats were fed a high (supplemented with 12 000 IU retinyl palmitate/kg) or a low (no supplementation) vitamin A diet for 14 weeks. Four animals in each dietary group were then challenged with [14C]3MI. The remaining four animals served as controls. Enzyme assays were performed and severity of the 3MI-induced lung damage was scored. Consumption of the low vitamin A diet resulted in a significant reduction in the liver and lung contents of vitamin A; however, serum concentration of vitamin A was unaffected. High vitamin A supplementation did not alter the activity of the MFO system. Clinical signs, lung – body weight ratio and wet – dry weight ratio of the lungs of 3MI-infused goats were not significantly different; however, in the low vitamin A goats, the microscopic lesions such as the extent of alveolar epithelial hyperplasia were judged to be significantly more severe than those observed in the high vitamin A goats.

scholarly journals Vitamin A in diets for Nile tilapia

2009 ◽  
Vol 66 (6) ◽  
pp. 751-756 ◽  
Author(s):  
Daniela Ferraz Bacconi Campeche ◽  
Rodrigo Ramos Catharino ◽  
Helena Teixeira Godoy ◽  
José Eurico Possebon Cyrino
Keyword(s):  
Vitamin A ◽  
Nile Tilapia ◽  
Stocking Density ◽  
Retinyl Palmitate ◽  
Feed Consumption ◽  
Vitamin Supplementation ◽  
Dietary Vitamin ◽  
Farmed Fish ◽  
Performance Variables ◽  
Randomized Experimental Design

Dietary vitamin supplementation decrease stress caused by high stocking density, and boosts immunological system of farmed fish. A studied was carried out to determine vitamin A requirements of Nile tilapia (Oreochromis niloticus) in an all male group (13.8 ± 1.2 g) and a mixed sex population (9.8 ± 2.3 g). Fish stocked in 100-L plastic aquaria (26.0 ± 1.0ºC) were fed to near satiety, twice a day, seven days a week, during 75 days with vitamin A-free, semi-purified diets supplemented with 0; 600; 1,200; 1,800; 2,400; 3,000; 3,600; 4,200; 4,800 and 5,400 International Units (IU) of retinyl palmitate (30% vitamin A) per kg of diet in a completely randomized experimental design, factorial arrangement 2c10 (n = 4). Deficiency signs of vitamin A were observed in fish fed 0 to 1.200 IU vitamin A kg-1 diet; moderate signs were observed in fish fed diets with 1.800 to 3.600 IU vitamin A kg-1 diet; no interactions group*level (p < 0.05) were detected. Dietary levels of vitamin A up to 5.400 IU kg-1 influenced final weight and weight gain of fish (p < 0.05), but did not influence feed consumption (p > 0.05). A group effect was observed regarding all performance variables (p < 0.0001). Quantification of hepatic retinol (HPLC) detected vitamin A only in fish fed 5.400 IU retinol kg-1 of diet, therefore characterizing that dietary retinol was used and stored. The quantity of 5.400 IU of retinol kg-1 of diet is recommended for adequate nutrition of Nile tilapia.

scholarly journals Multiple cytochrome P-450 genes are concomitantly regulated by vitamin A under steady-state conditions and by retinoic acid during hepatic first-pass metabolism

2011 ◽  
Vol 43 (1) ◽  
pp. 57-67 ◽  
Author(s):  
A. Catharine Ross ◽  
Christopher J. Cifelli ◽  
Reza Zolfaghari ◽  
Nan-qian Li
Keyword(s):  
Gene Expression ◽  
Retinoic Acid ◽  
Steady State ◽  
Vitamin A ◽  
Dynamic Range ◽  
Dynamic Change ◽  
The Body ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Wide Range

Vitamin A (retinol) is an essential precursor for the production of retinoic acid (RA), which in turn is a major regulator of gene expression, affecting cell differentiation throughout the body. Understanding how vitamin A nutritional status, as well as therapeutic retinoid treatment, regulates the expression of retinoid homeostatic genes is important for improvement of dietary recommendations and therapeutic strategies using retinoids. This study investigated genes central to processes of retinoid uptake and storage, release to plasma, and oxidation in the liver of rats under steady-state conditions after different exposures to dietary vitamin A (deficient, marginal, adequate, and supplemented) and acutely after administration of a therapeutic dose of all- trans-RA. Over a very wide range of dietary vitamin A, lecithin:retinol acyltransferase (LRAT) as well as multiple cytochrome P-450s (CYP26A1, CYP26B1, and CYP2C22) differed by diet and were highly correlated with one another and with vitamin A status assessed by liver retinol concentration (all correlations, P < 0.05). After acute treatment with RA, the same genes were rapidly and concomitantly induced, preceding retinoic acid receptor (RAR)β, a classical direct target of RA. CYP26A1 mRNA exhibited the greatest dynamic range (change of log 26 in 3 h). Moreover, CYP26A1 increased more rapidly in the liver of RA-primed rats than naive rats, evidenced by increased CYP26A1 gene expression and increased conversion of [3H]RA to polar metabolites. By in situ hybridization, CYP26A1 mRNA was strongly regulated within hepatocytes, closely resembling retinol-binding protein (RBP)4 in location. Overall, whether RA is produced endogenously from retinol or administered exogenously, changes in retinoid homeostatic gene expression simultaneously favor both retinol esterification and RA oxidation, with CYP26A1 exhibiting the greatest dynamic change.

Sign in / Sign up

Export Citation Format

Share Document