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Vitamins & Hormones
The possible influence of vitamin A on the balance between SH and SS groups also seems relevant to this subject. Thus, vitamin A has no dramatic role to parallel that shown by vitamin E in the prevention of massive liver necrosis in animals deprived of protein. At the most, experiments have shown that there may be some interplay between the levels of the protein and vitamin A intakes in their combined effect on the condition of the anima.
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N quantity and quality on vitamin A utilization was studied by administering a large dose of vitamin A to rats at the start of the test and measuring the vitamin A remaining in the liver and kidneys after the test diets were fed for three weeks. Highest vitamin A content was observed in the livers of rats fed a protein-free diet. With an increase in the dietary protein there was a progressive decrease in the amount of vitamin A in the liver and an increase in the amount of vitamin A in the kidneys.
Amino acid supplementation of gluten and zein resulted in an improved growth rate, increased depletion of hepatic vitamin A and greater total utilization of the vitamin.
Abstract
Chronic vitamin A deficiency induces a substantial delay in the rates of weight and height gain in both humans and experimental animals. Therefore, we analyzed the effect of vitamin A deficiency on endogenous proteolysis and nitrogen metabolism and its reversibility with all-trans retinoic acid (RA).
Male weanling rats, housed in pairs, were pair-fed a vitamin A-deficient (VAD) or control diet until they were 60 d old. Conversely, the epididymal white fat:body weight ratio and the plasma concentrations of alanine aminotransferase and adiponectin were significantly higher in VAD rats, which also had hepatic macrovesicular lipid accumulations. The expression of the genes encoding urea cycle enzymes and their activities increased in VAD livers.
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The experimental design was previously described. Rna and free amino acids are modified. Glutamine, serine and threonine level decrease while phenylalanine and leucine increase in vitamin A deficients.
The half time for radioactivity accumulation was four times higher into total and ribosomal protein, two times higher into postribosomal supernatant protein in vitamin A deficient rats than in well-fed rats. The decay of acid soluble radioactivity was similar in the two groups, although protein synthesis was lowered by vitamin A deficiency. Sedimentation analysis in sucrose gradients revealed a lower proportion of higher ribosomes species in muscle of deficient rat than in normal ones, but ribosomes from deficients were more active for protein synthesis in vitro than ribosomes from well-fed rats.
The vitamin A deficiency decrease the muscle protein synthesis and lead to important changes on in vitro and in vivo ribosomal activit.