The plasma transport and metabolism of retinoic acid in the rat

Smith, John E.; Milch, Peter O.; Muto, Yasutoshi; Goodman, DeWitt S.

doi:10.1042/bj1320821

Cited by 155 publications

(57 citation statements)

References 22 publications

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“…Previous work demonstrated that RA is transported to a variety of tissues in VAD rats given small doses of RA (25). The highest levels of RA were detected in the liver, kidney, and intestine, whereas the lowest levels were detected in the testis and fat pads.…”

Section: Discussionmentioning

confidence: 92%

Retinoic acid is detected at relatively high levels in the CNS of adult rats

Werner

DeLuca

2002

American Journal of Physiology-Endocrinology and Metabolism

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Retinoic acid (RA) is essential for cellular growth and differentiation in developing and adult animals. The central nervous system (CNS) suffers developmental defects if embryonic levels of RA are too high or too low. The production and function of RA in adult brain are unclear. We report that RA is present throughout the brain and spinal cord of adult, vitamin A-deficient (VAD) rats treated with a physiological amount of all- trans-retinol. The hippocampus/cortex contained the highest proportion of RA in the brain (27.2 ± 2.9% of the organic phase radioactivity, and 23.5 ± 0.8% of the organic phase radioactivity extracted from spinal cord was RA). RA comprises a higher proportion of the retinoid pool in the CNS compared with amounts reported in other target tissues (E Werner and HF DeLuca. Arch Biochem Biophys 393: 262–270, 2001). However, RA is not preferentially transported from the blood to the brain. There were 2.90 ± 0.20 fmol RA/g tissue transported to the brain of VAD rats treated with 2.00 nmol [20-3H]all- trans-retinoic acid, but higher amounts of RA were delivered to the liver, testis, and spleen. Because RA is not transported preferentially to brain, this tissue likely synthesizes RA more efficiently than other target tissues.

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Section: Discussionmentioning

confidence: 92%

Retinoic acid is detected at relatively high levels in the CNS of adult rats

Werner

DeLuca

2002

American Journal of Physiology-Endocrinology and Metabolism

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“…Previous studies in the rat showed that vitamin A deficiency alone inhibits the release of RBP from the liver so that the plasma concentration declines to between 25 and 30 % of the normal level while the pool of RBP in the liver increases fourfold (Muto et al 1972; Smith, Muto et al 1973). In the protein and vitamin A doubly-deficient rat the pool of accumulated RBP in the liver is smaller than that for the solely vitamin A-deficient animal, as indicated by the lower peak value of plasma retinol-binding holoprotein (holoRBP) reached after its release from the liverwithin 3-5 h after the xdministration of retinol.…”

Section: )mentioning

confidence: 99%

The early changes in retinol-binding protein and prealbumin concentrations in plasma of protein–energy malnourished children after treatment with retinol and an improved diet

et al. 1980

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I . Changes in total retinol-binding protein (RBP), the holoprotein (holoRBP) and prealbumin (PA) concentrations have been monitored in plasma of thirty protein-and vitamin A-deficient preschool children from within a few hours up to 7 weeks after treatment with retinol and a good-quality protein diet.2. The children were classified into groups according to nutritional status as having either kwashiorkor, marasmus-kwashiorkor or marasmus, and given formula diets whose protein and energy contents increased stepwise from I g and 105 kJ/kg body-weight respectively up to 4 g and 733 kJ/kg body-weight after 4 weeks. Retinol was administered in the forms of retinyl palmitate either orally or intramuscularly.3. PA and total RBP were determined by electroimmunoassay procedures and the holoRBP by its fluorescence after separation from other plasma proteins.4. RBP in plasma of the vitamin A-deficient child is largely denatured and incapable of binding administered retinol, which must first be taken up by the liver before native holoRBP is released. An increased pool of native apoprotein accumulates in the liver during vitamin A deficiency which is released into plasma quickly after retinol uptake to form peak concentrations of total and holoRBP approximately 3 h after dosing intramuscularly and 6 h orally.5. The accumulated pool of RBP was highest in livers from the marasmus group and lowest in those from the kwashiorkor group, reflecting their relative capacities to synthesize plasma proteins.6. The mean plasma concentrations of total and holoRBP for the various groups were minimal 24-48 h after dosing with retinol and then improved almost linearly over the following week.7. Mean plasma PA concentrations of the various groups on admission were also in order of the severity of their malnutrition. There was little or no change in this protein concentration over the first 24 h after dosing with retinol, but thereafter the mean values rose almost linearly over 2 weeks. Albumin on the other hand changed little during the first week. The results show that PA is the more sensitive measurement of protein nutritional status.A number of studies have shown that the plasma concentrations of retinol and its carrier, retinol-binding protein (RBP) and prealbumin (PA) are reduced in protein-energy mal- After treatment with a massive dose of retinol and a better-quality protein diet the concentrations of the various components of the vitamin A transport system recovered to levels within the normal range after 1-2 weeks. None of these studies, however, examined plasma RBP concentration within a few hours after dosing with retinol.(The nomenclature used in this paper for the various forms of retinol-binding protein is as follows : retinol-binding protein (RBP) is total immunoreactive protein ; retinol-binding holoprotein (holoRBP) is native protein with its ligand retinol attached ; retinol-binding

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“…Although hepatic retinyl palmitate did not change in response to protein malnourishment, protein-deficient animals exhibited a large decrease (21.8 nmol/ g liver) in metabolically 'active' retinol. This change cannot arise solely from a reduction of retinol binding protein concentration in the liver tissue as Smith and coworkers estimated that the retinol binding protein concentration in the rat liver is about 120 μg/g liver [22]. Assuming that these are all holoproteins, the concentration of retinol attributable to retinol binding protein is only 5.7 nmol of retinol/ g liver.…”

Section: Discussionmentioning

confidence: 99%

Decreased hepatic retinyl palmitate hydrolase activity in protein-deficient rats

Tsin

Chambers

Garcia

et al. 1986

Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metaboli

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Abstract28-day-old weanling rats were fed a diet containing 3% casein as the only source of protein for eight weeks to induce protein deficiency. When compared to control animals (fed a diet containing 25% casein), these rats had significantly lowered body (5.2-fold reduction) and liver (2.5-fold reduction) weights. The circulatory level of retinol (nmoi per ml plasma) as well as retinol (nmol per g tissue) in the liver of these protein-deficient animals were also reduced significantly, although their liver concentration of retinyl palmitate (nmol per g tissue) was comparable to that of the control group. Assay of liver tissue for retinyl palmitate hydrolase activity revealed a 4-fold reduction (compared to that of control animals) of specific enzyme activity (nmol retinol formed per g protein per h). These findings suggest that severe protein deficiency results in a decreased hydrolysis of retinyl esters in the liver, which may be in part responsible for the reduced level of metabolically 'active' retinoids available for normal physiological functions.

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The plasma transport and metabolism of retinoic acid in the rat

Cited by 155 publications

References 22 publications

Retinoic acid is detected at relatively high levels in the CNS of adult rats

Retinoic acid is detected at relatively high levels in the CNS of adult rats

The early changes in retinol-binding protein and prealbumin concentrations in plasma of protein–energy malnourished children after treatment with retinol and an improved diet

Decreased hepatic retinyl palmitate hydrolase activity in protein-deficient rats

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