Loss Of Retinol Research Articles

Retinol and beta carotene content of indigenous raw and home-prepared foods in Northeast Thailand

Retinol and β-carotene contents of raw and home-prepared indigenous foods in Northeast Thailand were studied. The criteria used to select the vitamin A-rich foods were high retinol or β-carotene contents of the individual food items, the amount and frequency of consumption, preference of consumption and food availability. Items selected were chicken liver, chicken egg, ivy gourd, amaranth, swamp cabbage (Chinese), Chinese cabbage, pumpkin, yellow sweet potato and two traditional menu items, kang-nho-mai and om-kruang-nai-kai. Raw food items were purchased from the local market; the traditional cooking procedures of the community were duplicated in the laboratory. Retinol and β-carotene contents were determined prior to and following cooking using HPLC methodology. The results indicated that boiling intact chicken liver resulted in 5% loss of retinol; boiling with cutting into small pieces and grilling resulted in losses of 8 and 16%, respectively. Greater losses (43%) were observed for egg omelet compared to hard-boiled egg (11%). For vegetables, blanching resulted in 7–11% loss of β-carotene, while steaming, frying and boiling showed losses of 15, 18 and 43%, respectively. Traditional foods such as bambooshoot soup (Kang-nho-mai) and chicken organ soup (Om-kruang-nai-kai) exhibited β-carotene losses ranging from 6–21%.

Urinary retinol excretion and kidney function in children with shigellosis

BackgroundBackground: Acute infections, including diarrhea, are associated with an increased risk of vitaminA deficiency. Urinary retinol excretion during such infections may contribute to this risk. The mechanism accounting for urinary retinol loss has not been clearly defined. ObjectiveThis study attempted to determine whether urinary retinol loss in children with acute infection is associated with impaired kidney function, particularly impaired tubular protein reabsorption. DesignUrinary retinol excretion and kidney function were examined in 66 hospitalized children 5 mo to 5 y of age with acute Shigella dysentery. ResultsUrinary retinol loss occurred in 59% of children and was substantial (>0.1 mmol/d) in 8% of them. Children with more severe disease excreted higher concentrations of urinary retinol; those with a body temperature > 40 °C excreted a mean of 0.10 ± 0.18 mmol/d compared with 0.005 ± 0.008 mmol/d for other children (P < 0.0001). Children with more severe disease also had impaired tubular reabsorption of low-molecular-weight proteins [ß2-microglobulin and retinol binding protein (RBP)], although other measures of tubular and glomerular function were not similarly impaired. In multiple regression analysis, severity of disease indicators were the best predictors of tubular reabsorption of ß2-microglobulin (R2 = 0.53) whereas tubular reabsorption of ß2-microglobulin and RBP were found to be the best predictors of urinary retinol loss (R2 = 0.69). ConclusionsA significant amount of retinol was excreted in the urine in children with shigellosis: 8% excreted > 0.10 mmol/d(15% of the daily metabolic requirement). Impaired tubular reabsorption of low-molecular-weight proteins, such as RBP transporting retinol, appeared to be the cause of this urinary retinol loss. Am J Clin Nutr 1998;68:1095–103.

Increased urinary retinol loss in children with severe infections

Vitamin A deficiency is a major public health problem in many parts of the developing world, often due to deficient dietary intake. 1 Stephensen CB Alvarez Jo Kohatsu J Hardmeier R Kennedy Jr, JI Gammon Jr, RB Vitamin A is excreted in the urine during acute infection. Am J Clin Nutr. 1994; 60: 388-392 PubMed Google Scholar Common childhood infections may also contribute to the development of vitamin A deficiency by a variety of mechanisms. Gut helminth infections, diarrhoea, and respiratory infections decrease vitamin A absorption from the gut and studies in adults with sepsis and pneumonia in the USA 1 Stephensen CB Alvarez Jo Kohatsu J Hardmeier R Kennedy Jr, JI Gammon Jr, RB Vitamin A is excreted in the urine during acute infection. Am J Clin Nutr. 1994; 60: 388-392 PubMed Google Scholar and in children with diarrhoea in Peru 2 Alvarez JO Salazar-Lindo E Kohatsu J Miranda P Stephensen CB Urinary excretion of vitamin A in children with acute diarrhea. Am J Clin Nutr. 1995; 61: 1273-1276 PubMed Google Scholar show losses of retinol in the urine, with greater proportional losses occurring in adults with more severe disease. Healthy controls in these studies excreted little or no vitamin A. We assessed urinary retinol loss in children with infections of different severity in Bangladesh where vitamin A deficiency is common.

Dissection of multi-protein complexes using mass spectrometry: Subunit interactions in transthyretin and retinol-binding protein complexes

Complexes formed between transthyretin and retinol-binding protein prevent loss of retinol from the body through glomerular filtration. The interactions between these proteins have been examined by electrospray ionization combined with time-of-flight mass analysis. Conditions were found whereby complexes of these proteins, containing from four to six protein molecules with up to two ligands, are preserved in the gas phase. Analysis of the mass spectra of these multimeric species gives the overall stoichiometry of the protein subunits and provides estimates for solution dissociation constants of 1.9 +/- 1.0 x 10(-7) M for the first and 3.5 +/- 1.0 x 10(-5) M for the second retinol-binding protein molecule bound to a transthyretin tetramer. Dissociation of these protein assemblies within the gas phase of the mass spectrometer shows that each retinol-binding protein molecule interacts with three transthyretin molecules. Mass spectral analysis illustrates not only a correlation with solution behavior and crystallographic data of a closely related protein complex but also exemplifies a general method for analysis of multi-protein assemblies.

Dissection of multi-protein complexes using mass spectrometry: subunit interactions in transthyretin and retinol-binding protein complexes.

Complexes formed between transthyretin and retinol-binding protein prevent loss of retinol from the body through glomerular filtration. The interactions between these proteins have been examined by electrospray ionization combined with time-of-flight mass analysis. Conditions were found whereby complexes of these proteins, containing from four to six protein molecules with up to two ligands, are preserved in the gas phase. Analysis of the mass spectra of these multimeric species gives the overall stoichiometry of the protein subunits and provides estimates for solution dissociation constants of 1.9 +/- 1.0 x 10(-7) M for the first and 3.5 +/- 1.0 x 10(-5) M for the second retinol-binding protein molecule bound to a transthyretin tetramer. Dissociation of these protein assemblies within the gas phase of the mass spectrometer shows that each retinol-binding protein molecule interacts with three transthyretin molecules. Mass spectral analysis illustrates not only a correlation with solution behavior and crystallographic data of a closely related protein complex but also exemplifies a general method for analysis of multi-protein assemblies.

Decline in plasma retinol in unconjugated hyperbilirubinemia treated with bilirubin adsorption using an anion-exchange resin.

When an anion-exchange resin column (Plasorba BR-350) was used for the treatment of unconjugated hyperbilirubinemia, we found an unexpected decrease in plasma retinol (vitamin A) concentrations in a patient with type I Crigler-Najjar syndrome. The purpose of our study was to investigate the mechanism of this decrease in plasma retinol. When the patient's serum bilirubin exceeded the bilirubin binding capacity of 14.7 mumol bilirubin/g serum albumin (i.e., 720 mumol/L of bilirubin), abrupt deterioration of the patient's neurologic status (suppression in his gait and speech) occurred, so the need to apply plasmapheresis to reduce the unconjugated bilirubin was indicated. Blood was drawn from the radial artery at a flow rate of 160 mL/min and pumped into a membrane plasma separator at a rate of 40 mL/min. The plasma was passed through the bilirubin adsorbent column and returned to the venous blood line of the plasma separator. Plasma samples were taken at the inlet and outlet of the bilirubin adsorbent column before and after treatment. The concentration of unconjugated bilirubin in plasma was effectively reduced by the perfusion, but plasma retinol was coincidentally decreased by the perfusion to vitamin A deficiency levels. The patient's plasma retinol was 2,127 nmol/L at the beginning of therapy and decreased to 1,492 nmol/L after repeated adsorption treatments. As the amounts of decrease in retinol (912 +/- 123 nmol/L) after the perfusion were almost equal to those in retinol-binding protein (1,010 +/- 192 nmol/L), retinol may have been removed as a form of holo retinol-binding protein. Decreases in retinol and retinol-binding protein levels were also observed in low-density lipoprotein (LDL) apheresis with a dextran sulfate column (i.e., a cation-exchange resin column). In the patient with Crigler-Najjar syndrome, retinol taken dietarily was removed by plasmapheresis. However, the patient manifested no clinical symptoms associated with vitamin A deficiency, since his liver storage of retinol could supply the loss caused by plasmapheresis treatment. We should measure plasma retinol concentrations to evaluate the loss of retinol during plasmapheresis treatment coupled with an anion-exchange resin column.

Vitamin a depletion in hospital and clinic patients with acquired immunodeficiency syndrome - A preliminary report

The objective of this study is to assess the serum concentration and the urinary depletion of vitamin A in patients with AIDS with acute illness (hospitalized) and without acute illness (clinic attenders); and to examine the relationship of serum and urinary retinol levels with weight loss, patient survival, CD4 count, fever, and liver function. Serum and urinary retinol of 26 patients from the AIDS clinic or hospital of the University of Alabama at Birmingham (UAB) were measured using HPLC. Mean serum retinol was lower in hospital patients than in clinic attenders, although the difference was not statistically significant. However, urinary retinol loss was significantly higher in hospital patients than clinic patients (0.09± 0.12 vs. 0.04 ± 0.12, p=0.0193). There were significant correlations between urinary retinol excretion and body weight loss in clinic patients and between urinary retinol loss and high serum bilirubin levels in hospital patients. A significantly higher proportion of hospital than clinic patients lost body weight during the last month before recruitment into the study (p=0.039). Further, a significantly higher proportion of those who lost weight subsequently died than survived (p=0.015). Urinary loss of retinol was significantly predicted by increased body temperature (p=0.0069) and decreased CD4 count (p=0.0454) in clinic patients. No single variable predicted significantly the urinary retinol loss in hospital patients. The presence of acute illness in hospital patients with AIDS appeared to be a risk factor for low serum retinol and increased urinary excretion of retinol. Greater urinary retinol loss and more severe illness are associated with body weight loss and death.

The kinetics of the loss of all-trans retinol at low and intermediate water activity in air in the dark

All-trans retinol was suspended on a support of microcrystalline cellulose and stored in air in the dark after equilibration at water activities from 0.11 to 0.75. The loss of all-trans retinol was monitored by normal phase HPLC. The rate of loss could be satisfactorily described by first-order kinetics with respect to all-trans retinol (up to more than 50% loss). The rate increased with increasing water activity in the range 0.11–0.75 a w. Arrhenius activation energies were found to be in the range of 28–48 × 10 3 J mol −1. A correlation between enthalpy change and Gibbs free energy change indicated a chemical compensation effect in the range 0.11–0.66 water activity.

Retinol and β‐carotene concentrations in skin, papillomas and carcinomas, liver, and serum of mice fed retinoic acid or β‐carotene to suppress skin tumor formation

Using 7,12-dimethylbenz[a]anthracene as the initiator and 12-O-tetradecanoyl-13-acetate as the tumor promoter on the dorsal skin of Sencar mice, we previously showed that pharmacological dietary all-trans-retinoic acid and beta-carotene inhibit the conversion of papillomas to carcinomas in a two-stage system of chemical carcinogenesis. The purpose of this study was to determine the influence of dietary retinoic acid and beta-carotene on retinoid and beta-carotene concentrations in skin and other tissues. We were unable to measure tissue retinoic acid because of the relatively limited amount of tissue available for analysis and the fast rate of metabolism. Different dietary levels of retinoic acid or beta-carotene did not influence total retinol of skin, papilloma, and carcinoma tissues, which all showed a concentration of approximately 1 +/- 0.5 microgram/g wet wt. Equally refractory to dietary retinoic acid or beta-carotene was serum retinol concentration. In contrast, dietary retinoic acid protected loss of liver retinol and retinyl palmitate, and beta-carotene caused an increase in beta-carotene and retinyl palmitate in liver but did not affect serum and liver retinol. We further investigated metabolic and functional aspects of retinoic acid in cultured mouse epidermal keratinocytes (LC-8 cells) and found that these cells actively metabolized [10,11-14C]retinoic acid to polar compounds. Isomers of retinoic acid were a minor product in the presence of cells and the major product when incubated in serum-containing medium in the absence of cells. From the functional point of view, exposure of LC-8 cells to 3 x 10(-6) M all-trans-retinoic acid (RA) caused a 75-fold induction in tissue transglutaminase and an approximately 9-fold induction in 10(-6) M RA at three days of culture. We conclude that retinoic acid spares endogenous retinol and that beta-carotene greatly enhances liver retinyl palmitate levels. Moreover we show that although mouse epidermal cells metabolize retinoic acid at a very high rate, they respond functionally by induction of tissue transglutaminase activity. Because this enzyme has been suggested to be involved in programmed cell death, we are presently investigating the possibility that it may be involved in the inhibition of carcinogenesis in mice fed pharmacological doses of RA.

Stability of retinol in milk during frozen and other storage conditions.

The effect of storage temperature and storage time on the retinol content of four commercial unfortified whole UHT milk samples was studied by HPLC. Significant losses of retinol in these milks were observed after 1 month of storage at 30 degrees C. Losses generally increased with storage time. Increasing the storage temperature from 30 degrees C to 40 degrees C had a variable effect depending on the particular milk. Short periods of frozen storage (up to 60 days) had no effect on the retinol content. However, frozen storage time from 4 to 8 months led to significant (P < 0.05) losses in retinol content. The effect of water activity and temperature conditions during storage of unfortified whole milk powder on the stability of retinol was also studied. Increasing the activity of water and temperature of storage significantly lowered the retinol content in milk powder.

Excessive faecal losses of vitamin A (retinol) in cystic fibrosis.

Vitamin A (retinol) deficiency is a recognised complication of cystic fibrosis and is presumed to be a consequence of an impairment in the digestion and absorption of dietary fats. The dietary intake of fat and retinol was assessed from a seven day weighed food intake in 11 subjects with cystic fibrosis and 12 matched controls. Faecal excretion of retinol and fat were measured from three day stool collections. There was little difference between the two groups in the intake of fat or retinol equivalents. When studied the subjects with cystic fibrosis were clinically stable and the apparent absorption of fat was not significantly different to that in the controls. There was a significant increase in the faecal losses of retinol in cystic fibrosis, which was unrelated to the degree of fat in the stool. In cystic fibrosis the median retinol recovered in the stool was 40% of the intake, compared with 1.8% in the controls. It is concluded that there is a specific defect in the handling of retinol by the gastrointestinal tract in cystic fibrosis, which may be unrelated to the digestion and absorption of dietary fat.

Retinol (vitamin A) and the neonate: special problems of the human premature infant

Retinol stores accumulate in fetal tissue during gestation. Hence, the premature infant faces extrauterine adaptation with less total reserves of retinol than does the term infant. Retinol-binding protein in serum is also lower in the premature infant population. The parenteral retinol supplementation frequently required for these infants has only recently become adequate by the finding of methods to avoid large losses of retinol onto intravenous tubing. Retinol is an essential vitamin for epithelial cell function; nearly 40% of lung cells are of epithelial origin. The premature infant's lung often is the initial site of difficulties during extrauterine adaptation, and respiratory system epithelial-cell damage and chronic lung disease frequently develop. Because these infants have associated low retinol reserves, retinol supplementation to help repair pulmonary injury is being considered. Some of these relationships are beginning to be clarified by basic research on the metabolism and function of retinol in lung.

Vitamin concentrations in very low birth weight infants given vitamins intravenously in a lipid emulsion: measurement of vitamins A, D, and E and riboflavin.

Because total parenteral nutrition with vitamins added to the glucose-amino acid mixture is often associated with a reduction in blood levels of vitamin A (retinol) during the routine treatment of many very low birth weight (VLBW) infants (less than 1500 gm), and because retinol losses in the plastic delivery system can be prevented by adding the vitamins to an intravenous lipid emulsion, seven VLBW infants with a mean birth weight of 900 gm (range 450 to 1360 gm) were given 40% of a unit dose vial, per kilogram of body weight, of a multivitamin preparation (M.V.I. Pediatric) (280 micrograms retinol; 160 IU vitamin D; 2.8 mg tocopherol; 0.68 mg riboflavin) in a lipid emulsion, Intralipid. After treatment with the intralipid-vitamin mixture for 19 to 28 days, plasma vitamin A (retinol) concentrations increased significantly from 11.0 +/- 0.76 (mean +/- SEM) before intralipid to 19.2 +/- 0.97 micrograms/dl after the intralipid-vitamin mixture (p less than 0.01); 25-hydroxyvitamin D concentrations increased from an initial value of 12.6 +/- 2.6 to 20.2 +/- 1.9 mg/dl (p less than 0.01); alpha-tocopherol concentrations increased from an initial value of 0.31 +/- 0.06 to 2.44 +/- 0.13 mg/dl (p less than 0.01); and riboflavin levels increased from 64.1 +/- 7.8 ng/ml to concentrations between 20 and 100 times the initial level. Erythrocyte riboflavin levels increased from 71.8 +/- 14 initially to 166 +/- 41 ng/gm hemoglobin, and erythrocyte flavin-adenine dinucleotide levels increased similarly from 972 +/- 112 initially to 2005 +/- 294 ng/gm hemoglobin. These results show that the addition of M.V.I. Pediatric to Intralipid decreases the extensive in vivo loss of retinol and is associated with an increase in plasma retinol concentrations in VLBW infants. The daily doses of vitamins D (160 IU/kg) and E (2.8 mg/kg) appear sufficient, but the dose of vitamin A (280 micrograms/kg) is insufficient to raise blood levels of all infants into the normal range. The current dose of riboflavin is excessive and may be harmful.

Retinoic Acid Supplementation of a Vitamin A-Deficient Diet Inhibits Retinoid Loss from Hamster Liver and Serum Pools

These studies were performed to follow a spectrum of relevant parameters in male Syrian golden hamsters fed either a vitamin A-deficient diet or the same diet supplemented with retinoic acid at 3 micrograms/g diet. Body weight and life span were not affected by the vitamin A-deficient diet until after 6-7 wk. Squamous metaplastic lesions of the Formalin-fixed tracheas were not generally observed in the hamsters fed the deficient diet until 6-7 wk, at which time blood retinol and liver retinyl palmitate levels had also decreased. Blood glucose levels remained normal (90 mg/dl) until about 7 wk but declined to about 40% of normal at 9 and 10 wk. Dietary retinoic acid supplementation of the vitamin-deficient diet (3 micrograms/g diet) inhibited the loss of retinol from blood and of retinyl palmitate from the liver so that these compounds were still present at 10 wk, but were not detectable in hamsters fed the vitamin A-deficient diet without retinoic acid.

The effect of 3,4,3′,4′-tetrachlorobiphenyl on plasma retinol and hepatic retinyl palmitate hydrolase activity in female Sprague-Dawley rats

A single ip dose of 1, 5, or 15 mg/kg 3,4,3′,4′-tetrachlorobiphenyl (TCB) caused a dose-dependent depression of plasma retinol levels 24 hr after treatment of female Sprague-Dawley rats. The loss of plasma retinol appeared to be a function of depressed levels of the retinol-retinol-binding protein (RBP)-transthyretin ternary complex. No free retinol-RBP was observed in plasma from treated animals. Hepatic retinyl palmitate hydrolase (RPH) activity was also depressed and highly and positively correlated to the plasma retinol levels. TCB was determined to be a noncompetitive inhibitor of partially purified RPH with a K I of 91 μ m. Incubation of TCB with liver microsomes and NADPH decreased the inhibition of RPH. Doses of either 2,4,5,2′,4′,5′-hexachlorobiphenyl (HCB) or 3,4,5,3′,4′,5′-HCB equimolar to the 15 mg/kg TCB dose failed to cause a similar depression of plasma retinol in treated female rats. We conclude that, unlike other polychlorinated biphenyl congeners, TCB causes a depression of plasma retinol by inhibition of hepatic RPH.

Persistently Low Blood Retinol Levels During and After Parenteral Feeding of Very Low Birth Weight Infants: Examination of Losses Into Intravenous Administration Sets and a Method of Prevention by Addition to a Lipid Emulsion

Very low birth weight infants have little storage of hepatic retinol and are, therefore, highly dependent upon an exogenous supply. The recent association between low serum retinol level and bronchopulmonary dysplasia and the persistently low serum levels of retinol during total parenteral nutrition prompted a prospective study to evaluate serial changes in serum retinol levels during 1 month of total parenteral nutrition (retinol dose 455 micrograms/d) and again during 1 month of total enteral feeding (retinol dose 200 to 300 micrograms/d) in the same infants. Infants were divided into two groups. Group 1 consisted of infants weighing less than 1,000 g (n = 24) and group 2 consisted of infants weighing 1,000 to 1,500 g (n = 17). Although initial mean levels of retinol were similar in both groups (14.8 +/- 0.9 and 13.5 +/- 0.7 micrograms/dL), there was wide variation between infants. In group 1 infants, there was a significant (P less than .01) decline in retinol level by the second week of life (to 9.2 +/- 1 micrograms/dL), which persisted during total parenteral nutrition, but increased to 13.4 +/- 2 after 1 week of enteral feeding. This level was maintained throughout enteral feeding. In group 2 infants, there was no significant change in serum retinol level throughout the study. During total parenteral nutrition, several infants had retinol levels below 10 micrograms/dL, a level associated with signs of retinol deficiency in older children. Because losses of retinol are known to occur in smaller volume total parenteral nutrition solutions, it was speculated that losses of retinol in our patients were due to retinol losses in the total parenteral nutrition delivery system.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a Pediatric Multiple Vitamin Preparation for Total Parenteral Nutrition II. Blood Levels of Vitamins A, D, and E

This study represents the first attempt to evaluate the American Medical Association Nutrition Advisory Group (NAG) recommendations for intravenous vitamin A, D, and E dosages for infants and children. Patients studied included 18 preterm infants (group 1) and 26 term infants and children (group 2A) receiving total parenteral nutrition for 2 to 4 weeks and eight infants and children receiving total parenteral nutrition for 3 to 6 months (group 2B). Term gestation infants and children up to 11 years of age all received the same dosages (those that were recommended by the NAG for children weighing more than 10 kg). Preterm infants received 65% of these doses. In group 1, cord blood alpha-tocopherol levels were less than 0.22 mg/dL in seven preterm infants (reference value = 0.29 +/- 0.04), but mean levels increased to 1.65 +/- 0.17 mg/dL after four days of treatment. Eight infants consistently received additional vitamin E orally (80 to 150 mg daily), and their levels increased to 2.18 +/- 0.26 mg/dL by four days of study and to 3.49 +/- 0.57 mg/dL after 3 weeks. Oral supplementation in the preterm infants appeared to be unnecessary because intravenous vitamins alone maintained levels above 1.1 mg/dL. In group 2, alpha-tocopherol levels were maintained within the reference range. Patients receiving lipid emulsions containing substantial quantities of alpha-tocopherol had significantly higher blood levels than patients receiving lipid emulsions containing little alpha-tocopherol (P less than .01). Mean 25-OH vitamin D levels were maintained above or within the reference range in groups 2A and 2B.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of vitamins a and e in serum and plasma using a simplified clarification method and high-performance liquid chromatography

A method of sample clarification and high-performance liquid chromatography specifically developed to permit precise and rapid determination of vitamin A (retinol) and vitamin E (α-tocopherol) in serum and plasma is reported. Serum proteins were denatured by the addition of acetonitrile containing α-tocopherol acetate, the internal standard; the vitamins were subsequently extracted into an organic matrix consisting of ethyl acetate—butanol (1:1); no solvent evaporation step was required. The three vitamins of interest were eluted from a reversed-phase C 18 column with an isocratic mobile phase methanol—water (95:5); detection was accomplished by measuring ultraviolet absorption at 280 nm. Recoveries of retinol, α-tocopherol and α-tocopherol acetate from spiked aqueous samples averaged 100.0, 100.0 and 98.8%, respectively. Recoveries of retinol, α-tocopherol and α-tocopherol acetate from plasma and serum relative to water were 102.6, 96.9 and 96.5%, respectively. Retinol and α-tocopherol were stable in the extraction matrix for up to 3.5 h, and were stable in heparinized plasma stored at room temperature for two days. Oxalate, citrate and EDTA caused significant losses of retinol and α-tocopherol, while vitamin levels in serum and heparinized plasma were similar. Limits of detection for retinol and α-tocopherol were 60 ng/ml and 0.9 μg/ml, respectively. Each run required 12 min. Same-day coefficients of variation were 3.5 and 3.6% for retinol and α-tocopherol, respectively ( n = 11). Betweenday coefficients of variation for retinol and α-tocopherol were 4.8 and 5.5%, respectively ( n = 5). This method permits simple, rapid, sensitive, selective and precise determination of retinol and α-tocopherol using 0.5 ml of serum or heparinized plasma.

Vitamin A losses to plastic intravenous infusion devices and an improved method of delivery

This study was designed to reevaluate the kinetics of vitamin A losses in the plastic intravenous infusion system used clinically in premature infants and to attempt to establish an improved method of delivery that would avoid significant and unpredictable losses. The losses of retinol, retinyl acetate, and retinyl palmitate were assessed in the presence of various concentrations of the emulsifier Tween 20. For a period of more than 24 h and at a concentration of 0.0085% Tween 20, retinol and retinyl acetate were delivered at 17.4 and 33.9% of the originally intended dose, respectively, while retinyl palmitate was at 100%. At 1% Tween 20, retinyl acetate was completely delivered but even at 2% Tween 20 only 51% of the retinol was delivered. The data suggest that predictable infusions of vitamin A may be attained by using retinyl palmitate rather than retinol in multivitamin preparations.

Determination of serum and plasma concentrations of retinol using high-performance liquid chromatography

An isocratic high-performance liquid chromatographic method specifically developed to allow simple and rapid determination of retinol concentrations in serum and plasma is reported. Retinol and retinol acetate (the internal standard) are extracted into butanol—ethyl acetate, with no subsequent evaporation step. Separation is achieved on a reversed-phase C-18 column, with a mobile phase consisting of acetonitrile—1% ammonium acetate (89:11), and UV detection at 313 nm. Recoveries of both retinol and the internal standard were 100%, and both compounds were stable in the extraction solvent for at least 2.5 h. Three anticoagulants (oxalate, citrate, EDTA) and perchloric acid (used in some methods to denature protein) all caused losses of retinol. Each run required 9 min; same-day coefficient of variation (C.V.) for identical samples averaged 2.5%; between-day C.V. was 6.4%; sensitivity was better than 10 ng/ml, while clinical concentrations were 400–1200 ng/ml. This method permits simple, rapid, sensitive, precise, and accurate determination of retinol using 0.5 ml serum or heparinized plasma.