The effect of high vitamin a intake on fatty acid composition of rat liver retinyl esters and total liver fatty acids

Comparative studies on lipid peroxidation of microsomes and mitochondria obtained from different rat tissues: effect of retinyl palmitate

The effect of retinyl palmitate on the polyunsaturated fatty-acid composition, chemiluminescence and peroxidizability index of microsomes and mitochondria obtained from rat liver, kidney, brain, lung and heart, was studied. After incubation of microsomes and mitochondria in an ascorbate Fe++ system (120 min at 37 degrees C) it was observed that the total cpm/mg protein originated from light emission: chemiluminescence was lower in liver microsomes, mitochondria and kidney microsomes in the vitamin A group than in the control group. In mitochondria obtained from control rats, the most sensitive fatty acids for peroxidation were arachidonic acid C20:4 n6 in liver and docosahexaenoic acid C22:6 n3 in kidney and brain. In microsomes obtained from control rats, the most sensitive fatty acids for peroxidation were linoleic acid C18:2 n6 and C20:4 n6 in liver and C22:6 n3 in kidney. Changes in the most polyunsaturated fatty acids were not observed in organelles obtained from lung and heart. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of fatty acids, showed significant changes in liver, kidney and brain mitochondria, while in microsomes changes were significant in liver and kidney. These changes were less pronounced in membranes derived from rats receiving vitamin A. Our results confirm and extend previous observations that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.

Fatty acid, carotenoid and vitamin A composition of tissues of free living gulls

The aim of this study was to investigate fatty acid and carotenoid profile as well as vitamin A (retinol and retinol esters) content in gull (Larus fucus) tissues. Palmitic (16:0) and stearic (18:0) fatty acids were major saturates in all the tissues studied. Oleic acid (18:1n-9) was the major monounsaturate in the tissue phospholipids varying from 11.9% (liver) up to 18.2% (lung). Arachidonic acid (20:4n-6) was the major unsaturate in the phospholipid fraction in all the tissues. Liver contained the highest total carotenoid concentration which was 5 and 7 fold higher compared to kidney and pancreas. In the liver beta-carotene was major carotenoid. In contrast, in all other tissues beta-carotene was minor fraction with lutein being major carotenoid. Zeaxanthin, canthaxanthin, beta-cryptoxanthin and echinenone were also identified in the gull tissues. Liver and kidney were characterised by the highest vitamin A concentrations (1067.5 and 867.5 microg/g, respectively). Retinol comprised from 55.3% (pancreas) down to 8% (kidney) of the total vitamin A but was not detected in the abdominal fat. Retinyl palmitate was the major retinyl ester in the liver, kidney and heart (44.2; 38.1 and 46.0% of total retinyl esters). In muscles and abdominal fat retinyl stearate was the major retinyl ester fraction. Therefore high proportions of beta-carotene were found in gull liver and peripheral tissues were enriched by lutein and zeaxanthin compared to the liver, a very high concentration of retinyl esters in the kidney was observed and tissue-specificity in retinyl ester proportions in peripheral tissues was found.

Vitamins A1 (retinol), A2 (3,4-didehydroretinol) and E (alpha-tocopherol) in the liver and blubber of lacustrine and marine ringed seals (Phoca hispida sp.)

Concentrations of vitamins A1 (retinol), A2 (3,4-didehydroretinol) and E (alpha-tocopherol) in the liver and blubber of ringed seals from Lake Saimaa (Phoca hispida saimensis), Lake Ladoga (P. h. ladogensis), the Baltic Sea (P. h. botnica) and Spitsbergen (P. h. hispida) were determined by high-performance liquid chromatography. The freshwater seals had much lower levels of vitamin A1 but higher levels of vitamin A2 than the marine seals. The concentrations of vitamin E in the livers of the subspecies studied were high compared with earlier reports of seals, but the ranges were large. The livers of the marine seals contained more vitamin E than the livers of the freshwater seals, but the levels in the blubber were uniform in all populations, except in old specimens from the Baltic. The differences between the freshwater and marine seals are suggested to be due mainly to diet. The ratios of A1 to A2 in the liver and blubber and in the fish diet were similar for the marine seals and for the freshwater seals (but differed in the marine and freshwater populations), which suggests no great differences in the absorption, transport and metabolism of the two analogues. Blubber was an important storage site for the vitamins studied, and age-dependent increases were detected, especially for vitamin E. In the 2-month to 2-year-old ringed seals of Lake Saimaa, however, the vitamin E concentration in the blubber was not affected by age.