Retinol tissue concentrations

Biesalski, FI. K. (1996). Effects of intratracheal application of vitamin A on concentrations of retinol derivates in plasma, lungs and selected tissue of rats. Int. ]. Vitam. Nutr. Res. 66, 106-112. 

Nierenberg, D.W. Nairn, S.L. 1992. A method for determining concentrations of retinol, tocopherol, and five carotenoids in human plasma and tissue samples. Am. J. Clin. Nutr. 56 417-426. 

The DNA adducts, deoxyadenosine and deoxygua-nosine, which are induced by malondialdehyde, the end-product of lipid peroxidation, accumulate in human breast tissues. These adducts are present at relatively higher concentrations in breast cancer cells compared to normal breast cells. In a recent study, serum antioxidative vitamin levels and lipid peroxidation were compared in gastric cancer patients. The level of serum ascorbic acid, a-tocopherol, p-carotene, and retinol were assessed. The levels of ascorbic acid in patients with gastric carcinoma were less than one-fifth of that in the control group, and the production of p-carotene and a-tocopherol were decreased, as well. 

Palozza, P. 1998. Prooxidant actions of carotenoids in biologic systems. Nutr. Rev. 56(9) 257-265. Parker, R.S. 1996. Absorption, metabolism and transport of carotenoids. FASEB J. 10 542-551. Peng, Y.M., Peng, Y.S., Childers, J.M., Hatch, K.D., Roe, D.J., Lin, Y. and Lin, P. 1998. Concentrations of carotenoids, tocopherols and retinol in paired plasma and cervical tissue of patients with cervical cancer, precancer and noncancerous diseases. Cancer Epidemiol. Biomark. Prev. 7 347-350. 

Oxidation of retinol produces retinoic acid tretinoin). The reaction is irreversible. Retinoic acid enters the portal blood, is transported bound to albumin, and is not stored to any great extent. The concentration of retinoic acid in plasma is normally 3-4 ng/mL. A biologically active metabolite, 5,6-epoxyretinoic acid, has been isolated from the intestinal mucosa of vitamin A-deficient rats following administration of H-retinoic acid. Several tissues have specific cellular retinoic acid-binding proteins (CRABPs). 

FIG. 1. Relationships among the model, the system under investigation and the experimental observatimis. EHT = extiahepatic tissue ROH = retinol /3-Car = /S-Carotene. Isotopomer ratios of /S-carotene-dji/ -carotene and retinol-dVretinol and the concentrations of total fi-carotene and total retinol in plasma by time since ingesting /3-carotene-dg (the experimental measurements) are shown in the bottom left and right panels, respectively. Rudiments of the mottel include the compartment the fractionid transfer coefficient and flow from a donor to a recipient compartment the initial conditions of the system and a set of rules for relating elements of the model with the experimental observations made on the system under investigation. 

FIG. 7. Compartmental model predicted masses and concentrations of retinol and retinyl ester in plasma, liver, and extrahepatic tissue of a healthy adult who ingested a single 73-/imol dose of /S-carotene-dn orally. The Fast turnover liver retinoid (bottom left) and Slow turnover liver retinoid (bottom right) each include the protio and deuterated species. 

An exposure time of 2 h is sufficient to induce an effect on morphogenesis and gene expression and avoids the complication that deleterious effects on the yolk sac placenta may affect development if RA is present throughout the whole culture period. The required concentration and exposure time need to be worked out by using a range of concentrations and times for each new experiment. Hindbrain defects can be induced by a concentration of 0.25 pg/mL medium. For this, dissolve 1 mg RA in 0.8 mL Analar ethanol and add 1 pL of this solution to 5 mL culture medium. To conPol cultures, 1 mL ethanol should be added. This amount of ethanol is insufficient to cause abnormalities and probably evaporates rapidly at 38°C. Some laboratories use DMSO as a solvent for RA (11). RA should always be added to the medium before the embryos are added. After exposure, embryos should be washed in Tyrode saline (do not use PBS, because they require calcium for normal morphogenesis) and replaced in fresh culture medium. Both RA and retinol can similarly be inttoduced to the tissue-culture medium of embryonic cell, tissue, and organ cultures. 

Fig. 2. HPLC analysis of neutral retinoids in tissues and plasma Samples were eluted from a reverse-phase Waters ODS column (1.2 x 10 cm) at 2 mL/min with a linear gradient of 15% water in methanol to methanol over 20 min, followed by 30 min of methanol. 1, 5,6-epoxyretinol 2, aU-trans-retinol, 3, all-/ra -retinal, 4, anhydroretinol, 5, retinyl docosahexanoate 6, retinyl palmitoleate 7, retinyl linoleate 8, retinyl palmitate and retinyl oleate, 9, retinyl stearate These specific examples illustrate the analyses of neutral-tissue retinoids equilibrated with orally fed [ HJretinol and extracted from (A) rat small-intestine mucosa (dashed line) or kidney (solid line) (B) plasma (dashed line) or liver (solid line) The concentrations of retinol and most retinyl esters in tissues and blood, however, are sufficiently large for detection by UV at 325 nm.

Repletion of retinol-deficient rats can also be effectively achieved by the intravenous injection of retinol dispersed in a 20% Tween 40 solution (Smith et al., 1980 Fig. 4). Such an injection produces a rapid, dose-related increase in the serum concentration of RBP. The changes in serum RBP levels seen after the injection of retinol in a 20% Tween 40 solution closely resembled those previously seen after the injection of vitamin A (retinyl esters) in association with lymph chylomicrons. However, the amount of retinol required to stimulate the secretion of a given amount of RBP from the liver was about two to three times that required when retinol (retinyl esters) was injected in chylomicrons. As discussed by Smith et al. (1980), this quantitative difference is probably due to differences in the tissue distribution pattern of retinol when injected in the Tween 40 solution, compared to its administration in the form of chylomicrons. 

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