Vitamin A-deficient Rats Research Articles

The Effects of Chylomicron Vitamin A on the Metabolism of Retinol-binding Protein in the Rat

Abstract Vitamin A-deficient rats have low levels of retinol-binding protein (RBP) in serum and elevated levels of RBP in their livers. Chylomicrons containing newly absorbed vitamin A were injected intravenously into vitamin A-deficient rats, and the levels of vitamin A and of RBP in serum were determined on samples collected serially from individual rats. Data were also obtained on liver immunoreactive RBP concentrations with samples obtained at death. Chylomicrons were used so that the vitamin could be administered physiologically, in the form in which it is normally absorbed. After the injection of chylomicrons containing vitamin A a rapid increase in the serum levels of RBP and of vitamin A occurred, with maximal levels observed at 2 to 4 hours. The magnitude of the response was directly related to the amount of vitamin A given, in the dose range 0 to 17 µg of vitamin A. In an initial study of the dose range of 0 to 32 µg, a maximal response was obtained with doses of 16 µg or greater. Substantial increases in serum RBP levels were observed soon after chylomicron clearance, by 45 min after chylomicron injection. Livers were obtained 2 hours after chylomicron injection in rats given graded amounts of vitamin A. The dose-response relationship of the increase in serum RBP was mirrored by a complementary dose-related decrease in the level of RBP in the liver. Release of RBP from liver into serum, which was a function of the amount of vitamin A given, apparently occurred. Rats pretreated with either puromycin or cycloheximide also showed a rapid and substantial rise in serum RBP and vitamin A levels, after the injection of vitamin A. The results indicate that the increased level of RBP in serum after vitamin A injection mainly represents the release of previously formed RBP from an existing pool in the liver, rather than representing newly synthesized protein. The secretion of RBP by the liver is regulated efficiently by the availability of vitamin A for the formation of the retinol-RBP complex.

Transfer ribonucleic acid of vitamin A-deficient rats

The effect of vitamin A deficiency on the chromatographic elution patterns of liver tRNA from BD-cellulose was investigated. The tRNA and aminoacyl-tRNA synthetase enzymes were prepared from the liver of normal (control) and vitamin A-deficient rats. Following deacylation, tRNA from both sources was charged with an l-[3H]-amino acid mixture using homologous and heterologous synthetase preparations. The tRNA was also charged individually with the two essential amino acids, l-[3H-methyl]methionine and l-[3H] phenylalanine, using homologous synthetase enzymes. The elution profiles of labeled aminoacyl tRNA's from BD-cellulose columns were subsequently determined. The degree of acylation of tRNA from vitamin A-deficient rats was always greater than that of normal tRNA, regardless of the source of enzyme preparation. The elution patterns from BD-cellulose of charged tRNA showed that synthetases from deficient animals acylate certain normal tRNA species which normal enzymes seem not to acylate, and that normal synthetases also acylate distinct vitamin A-deficient tRNA species. Furthermore, the elution pattern of normal tRNAphe differed from that of deficient tRNAphe in the number of eluted peaks and in their relative elution position. Whereas, in the normal case, two tRNAmet peaks were eluted in the deficient state, only one tRNAmet peak was observed.

Apparent Turnover of Subcellular Phospholipids in the Liver of Control and Vitamin A-deficient Rats

The half-lives of phospholipids derived from microsomes, mito chondria and soluble fractions of livers from control and vitamin A-deficient rats after the administration of 14C-labeledcholine, ethanolamine, glycerol, and pal mitic acid have been determined. The half-lives of subcellular phospholipids from control animals labeled with either choline, glycerol or palmitic acid were statis tically similar (22 to 36 hours), whereas those phospholipids labeled with etha nolamine had significantly shorter half-lives (14 to 16 hours). No significant differences were noted between the half-lives of phospholipids from control and deficient subcellular fractions. J. Nutr. 102: 1465-1470, 1972.

Studies on the incorporation of (U- 14 C)glucose into intestinal lipids in vitamin A-deficient rats.

Studies on the incorporation of (U- 14 C)glucose into intestinal lipids in vitamin A-deficient rats.

RNA metabolism in rat intestinal mucosa of normal and vitamin A-deficient rats

The decreased rate of leucine incorporation into leucyl-tRNA by the pH 5 enzyme fraction from vitamin A-deficient rat intestinal mucosa was investigated. When tRNA from either normal or vitamin A-deficient rat intestinal mucosa was added to the vitamin A-deficient pH 5 enzyme fraction, the yield of leucyl-tRNA rose to normal levels. Freon column chromatography of iso-accepting leucyl-tRNAs and threonyl-tRNAs failed to show any qualitative difference between normal and vitamin A-deficient iso-accepting species. Hence, a decrease in the amount of tRNA available for charging is responsible for the decrease in charging activity of the pH 5 enzyme fraction from vitamin A-deficient rat intestinal mucosa. RNA synthesis in the intestinal mucosa of normal and vitamin A-deficient rats was studied after intraperitoneal injection of either 14C-6-orotic acid or 3H-G-uridine. In three experiments the amount of label incorporated into all RNA fractions was 30–45% higher in the vitamin A-normal than the vitamin A-deficient rats. Measurements of uridine, UMP, and UDP pool sizes and their specific radioactivities 1 hr after injection of the label revealed that the difference in RNA synthesis between normal and vitamin A-deficient rat intestinal mucosa represented a true difference in the incorporation of the label into RNA and not a dilution effect on the label in deficient rats.

The metabolism of retinyl methyl ether in the rat in vivo.

1. Retinyl methyl ether was converted into vitamin A in vitamin A-deficient rats regardless of whether administered by oral, intraperitoneal, intramuscular or subcutaneous route; intramuscular administration seemed to be the best for conversion as well as storage. 2. Significantly, unchanged retinyl methyl ether was also found in the liver after oral administration but not after administration by other routes. 3. Oral administration of 1mg of retinyl methyl ether led to a progressive increase in liver vitamin A with time reaching a value of 16% of administered dose after 24h. No retinyl methyl ether was detectable in liver at any time-interval in this experiment. 4. Conversely, oral administration of 4mg of retinyl methyl ether/day for 4 days led to the accumulation of 25% of the dose as unchanged retinyl methyl ether in the liver 1 day after the last dose; however, it was gradually but completely converted into vitamin A over a period of 18 days. 5. The significance of these findings with special reference to the fundamental metabolism of vitamin A, the site of conversion of retinyl methyl ether into vitamin A, the relative efficiency of various routes of administration and its biological activity are discussed.

Influence of Dietary Vitamin A Level on Chicken Liver Glycogen

THERE are conflicting reports concerning the effect of a vitamin A deficiency on liver glycogen. Wolfe et al. (1957) reported that liver glycogen was essentially zero in vitamin A-deficient rats compared to a relatively high level in controls. Stoewsand and Scott (1964) found that liver glycogen formation during the first four hours of refeeding a high protein diet to chicks after a one-day fast was not impaired by a vitamin A deficiency. Their results indicated that vitamin A-deficient chicks fed a moderate protein level had a higher liver glycogen content per gram of feed consumed than the vitamin A adequate controls. Perek and Kendler (1969a) reported that fasted and nonfasted mildly vitamin A-deficient chicks were hyperglycemic and had liver glycogen concentrations reduced to less than half that of contols. Singh et al. (1968) reported that nonfasted hypervitaminotic A rats were no different in liver glycogen levels than controls. However, the…

Visual pigments of the vitamin A-deficient, thyroidectomized rat following vitamin A 2 administration

Thyroidectomized, vitamin A deficient rats suffered a loss of visual sensitivity, as determined by the electroretinographic b-wave, and a loss of rhodopsin, as determined by extraction. The results were similar to those obtained with rats having intact thyroid glands. These visual deficiencies were repaired by giving crystalline vitamin A 2 (3-dehydroretinol). In thyroidectomized animals, as in normal animals, the visual pigment was restored; this pigment was not a porphyropsin, but normal rat rhodopsin (P498 1) with a minor component of a P517 2. Thyroidectomy, therefore, did not alter the normal conversion of 3-dehydroretinol to retinal which we believe occurs in the vitamin A-deficient rat given vitamin A 2. The results are compared with published data on the effects of thyroid hormone on visual pigment conversion in bullfrog tadpole and certain fishes. It is concluded that no general role has yet been established for the thyroid in the conversion of visual pigments between the two classes.

Influence of Vitamin A Deficiency on Tissue Glycogen Metabolism in Growing Chickens ’

VITAMIN A has been reported to alter certain aspects of carbohydrate metabolism. Wolf et al. (1957) found an interference in gluconeogenesis in the intact vitamin A-deficient rat. Acetate, lactate and glycerol carbon incorporation into liver glycogen was severely reduced in vitamin A-deficient rat livers with thpre being essentially no liver glycogen in the A-deficient rats. Perek and Kendler (1969) reported decreased liver glycogen levels in vitamin A-deficient chicks. Stoewsand and Scott (1964) reported that high dietary protein and vitamin A deficiency had an effect upon liver glycogen which may indicate an abnormal turnover of liver glycogen in vitamin A-deficient chicks. Unpublished results of Nockels at this laboratory suggested an impairment in lactic acid formation from glycogen in the pectoralis muscles of mildly vitamin A-deficient chickens.The present research was undertaken to study the effect of vitamin A deficiency on glycogen degradation in the white muscles of the pectoralis major and…

Formation of retinoic acid from retinol in the kidney

Retinoic acid was formed in the kidney of vitamin A-deficient rats after the administration of a physiological dose of retinyl acetate. It appeared in the kidney before it could be detected in the blood plasma. It was also found in greater proportion as the retinyl acetate dosage was decreased. These findings support the hypothesis that retinoic acid may be the metabolically active form in the growth function of vitamin A.

Turnover of mammalian phospholipids. Rates of turnover and metabolic heterogeneity in cultured human lymphocytes and in tissues of healthy, starved and vitamin A-deficient rats.

1. Choline- and inositol-labelled phospholipids of human cultured lymphocytes turn over in a biphasic manner; phytohaemagglutinin activation stimulates turnover. 2. Choline-labelled phospholipids of rat liver and kidney, but not of blood, turn over in vivo as fast as those of duodenum, ileum or colon. Turnover in the intestinal tissues is greater in fed than in starved or vitamin A-deficient rats. In each case phosphatidylcholine turns over relatively faster than sphingomyelin or lyso-phosphatidylcholine. 3. It is concluded that phospholipid turnover of the type described is a common feature of viable cells, and that metabolically favourable conditions increase, rather than decrease, turnover.

Biosynthesis of a Fucose-containing Glycopeptide from Rat Small Intestine in Normal and Vitamin A-deficient Conditions

Abstract The number of goblet cells in the small intestine decreased in the vitamin A-deficient rat. Incorporation of 14C-d-glucosamine into a fucose-containing glycopeptide declined markedly. Ultracentrifugation of this glycopeptide in H2O gave only a single component, with a sedimentation value of 3.6 S, whereas, in 0.1 m phosphate buffer (pH 7.5) two components appeared, with much higher sedimentation constants (6.2 S and 7.2 S). The glycopeptide was found to contain glucosamine, galactose, fucose, and sialic acid in the molar ratios of 3:3:1:0.25, respectively. Synthesis of the fucose-containing glycopeptide in vitro, using uridine-diphosphate-N-acetyl-d-glucosamine-1-14C and 3H-serine, showed a 2- to 3-fold decrease in the incorporation of the labels by rough endoplasmic reticulum prepared from vitamin A-deficient animals as compared with normal animals.

Vitamin A and ribonucleic acid synthesis in rat intestine

The incorporation of ( 3H)-5-orotic acid into ribonucleic acid of colon and small intestinal mucosa of vitamin A-deficient rats was stimulated 1.5- to 3.0-fold 2–5 hr after the intravenous administration of retinol. The stimulation was most pronounced in the RNA isolated from the nuclear fraction.

Scanning electron microscopy of the retina in vitamin A-deficient rats.

The retinal changes occurring in vitamin A-deficient rats were investigated with the aid of a scanning-electron-microscope.

The effect of calorie and protein malnutrition on both the parasite and the host in acute murine schistosomiasis mansoni.

Schistosomiasis mansoni occurs in areas of the world in which malnutrition is rife. Nevertheless, relatively little laboratory experimentation has been performed on the effects of various nutritional deficiencies on this major parasitic disease. The few previous studies have in general been devoted to the effect of malnutrition on either the parasite or the host but not on the interaction between them. Krakower et al. [1, 2], working with poor natural hosts [3], observed that developing Schistosoma mansoni worms were not destroyed as rapidly in vitamin A-deficient rats as in wellnourished controls, and that the worms in scorbutic guinea pigs produced defective egg shells. DeWitt [4, 5], feeding mice (good natural hosts) a diet deficient in selenium, vitamin E, and cystine, noted that more worms developed, but that they were immature and did not produce eggs. DeMeillon and Paterson [6], stimulated by DeWitt's studies, recorded their impression that mice on a 12.8 ^j protein diet passed relatively few eggs in their feces.

Vitamin A and Nuclear RNA Synthesis

It appears that vitamin A administration to vitamin A-deficient rats very rapidly increases uridine incorporation into intestinal mucosal RNA and into liver rapidly labeled nuclear RNA.

VIsual pigments of the vitamin A-deficient rat following vitamin A 2 administration

Male albino rats (Sprague-Dawley) were depleted of vitamin A and then given crystalline vitamin A 2 as supplement. During depletion the growth and general tissue functions were maintained in normal state by means of retinoic acid. The status of the retina during depletion and recovery was monitored by histological and electroretinographic examinations. It was found that vitamin A 2 restored the normal retinal histology and the normal ERG threshold. Examination of the photopigment content in the retinas of these rats revealed the presence of a major component, which was normal rat rhodopsin, and a minor component that absorbed maximally at 517 nm and contained 3-dehydroretinal as the prosthetic group. The experiment was controlled by using rats without vitamin A supplementation and rats supplemented with all- trans vitamin A 1. The former showed very small quantities of photopigment; the latter showed normal rat rhodopsin. It was concluded that a conversion of vitamin A 2 to retinal occurs in the rat, leacling to the formation of normal rhodopsin, although a small amount of 3-dehydroretinal is also produced leacling to the formation of the 517 pigment.

The Effect of Ascorbic Acid on the Carbohydrate Metabolism of Vitamin A-Deficient Chicks

INTRODUCTIONIMPAIRMENT of glucocorticoid production in vitamin A-deficient rats was reported by Johnson and Wolf (1960); they attributed to vitamin A a co-enzyme function in adrenal glucocorticogenesis. Hepatic glycogen increased in response to cortisone administration (Greengard et al. 1963). Injections of ACTH, exposure of birds to shaking or to infection resulted in an enhanced glycaemia and in a decreased concentration of glycogen in the liver (Juszkiewicz et al., 1964). Stimulation of adrenal weights and an increased synthesis of 21 α-ketol responsive corticosteroids in the adrenals of vitamin A-deficient chicks was recently reported by the authors (Perek and Kendler, 1969).Dietary administration of ascorbic acid (AA) was reported to have a benevolent influence upon hens under climatic stress (Perek and Kendler, 1963; Lyle and Moreng, 1968), and a sparing effect upon vitamin A (Kendler and Perek, 1968).The present research therefore was designed to examine possible changes in the carbohydrate level…

Purification and properties of the enzyme ATP-sulfurylase and its relation to vitamin A

1. 1. The enzyme ATP-sulfurylase which catalyzes the formation of adenosine 5′-phosphosulfate (APS) was purified about 1000-fold over supernatant fraction by ammonium sulfate and acid precipitation and by elution from Sephadex G-200, agarose and hydroxyapatite columns. 2. 2. The molecular weight of the enzyme was between 800 000 and 900 000; its optimum pH, at 8.0; its K m with respect to ATP, 1.6 · 10 −3M; K m (sulfate), 1.0 · 10 −4M; K m (APS), 2.5 · 10 −4 M; K m (PP 1), 3.7 · 10 −5M. There was inhibition at high PP 1 and APS concentrations and at low concentrations of ADP. Cu 2+ and Co 2+ were strongly inhibitory. p-Chloromercuribenzoate (PCMB) and EDTA also inhibited: the former inhibition was completely relieved by glutatione; the latter, by Mg 2+. The enzyme was irreversibly inactivated by deoxycholate. It was unstable in Tris-HCl buffer and decayed to about 15% activity in 24 h whether measured by ATP generation or molybdolysis. It was completely stabilized by phosphate but not by barbiturate or sulfate ions. 3. 3. The mechanism of the reaction was explored by a study of the reaction kinetics and the following was observed: (a) the rate of exchange of 32PP i into ATP was greater in presence than in absence of sulfate and greater (even in absence of SO 4 2− than the overall reaction of APS synthesis; (b) there was no exchange of 35SO 4 2− into APS in presence or absence of PP 1; and (c) the rate of reaction of APS with P i at low APS concentrations was independent and at high concentrations was dependent on PP i concentration. We conclude that the reaction proceeds through intermediate formation of an AMP-enzyme complex. 4. 4. 14C-Labeled vitamin A was administered to vitamin A-deficient rats, and ATP-sulfurylase was isolated after 3 days. Although radioactivity remained associated with the enzyme over some of the purification steps, highly active enzyme which had lost all radioactivity was obtained by fractionation on agarose columns. Similar results were obtained when the labeled vitamin was homogenized with rat embryo livers or injected into newborn rats. We conclude that neither vitamin A nor a metabolite of the vitamin is an integral or necessary part of the enzyme and suggest that since the enzyme is unstable, particularly under conditions of low phosphate concentration, vitamin A may help to stabilize the enzyme.

Vitamin A and the biosynthesis of sulphated mucopolysaccharides. Experiments with rats and cultured neoplastic mast cells.

1. The uptake and incorporation of [(35)S]sulphate into mucopolysaccharides by colon and duodenum in vitro are unaffected by the vitamin A status of the animals. 2. Uptake and incorporation in vivo are unaffected at 4hr. after injection of [(35)S]sulphate, but at later times are decreased in some tissues of vitamin A-deficient animals. 3. The rate of removal of (35)S from blood, its rate of appearance in urine, the plasma concentration of sulphate and the uronic acid content of several tissues are not significantly altered in vitamin A deficiency. 4. These results, and direct measurement of (35)S in mucopolysaccharides at various times after injection of [(35)S]sulphate, suggest that the synthesis of mucopolysaccharides is unaffected but that their turnover is increased in vitamin A deficiency. 5. Neither the growth rate of, nor the incorporation of [(35)S]sulphate into heparin by, P815Y and HC cultured neoplastic mast cells is decreased when the horse serum necessary for growth is treated with ultraviolet light or is replaced by serum from vitamin A-deficient rats. 6. The addition of citral is no more toxic to growth rate or to incorporation of (35)S than is the addition of vitamin A itself. 7. It is concluded that neoplastic mast cells in culture do not require vitamin A for growth or for the synthesis of heparin. 8. None of these results is compatible with the view that vitamin A or a derivative is directly involved in the biosynthesis of sulphated mucopolysaccharides.