B6-deficient Rats Research Articles

Effects of Dietary Vitamin B6 on the Utilization of Monosodium Glutamate by Rats

The absorption and utilization of monosodium L-glutamate (MSG) have been studied in control and vitamin B6-deficient rats. When 1 mg of labeled or unlabeled MSG/gram of body weight was administered intraduo- denally, higher plasma glutamate but not 14Clevels were observed in the jugular and portal blood of deficient rats than controls. This appeared to be related to decreased tissue utilization and intestinal transaminatA­on of glutamate in de ficient animals. Vitamin B6 deficiency resulted in a delayed clearance from plasma of intravenously administered glutamate. Aspartate and alanine amino- transferases, the two major glutamate transaminases of the intestinal mucosa were measured in pre- and postweanling rats. The activity of these enzymes was low in rats under 21 days of age. They were not affected by pyridoxine adminis tration. Following weaning intestinal transaminase activity was markedly in creased by the feeding of diets with adequate vitamin B6 and further decreased by diets deficient in the vitamin. These studies point up the need in MSG toxicity studies to especially consider the age and state of vitamin B, nutriture of the animals used and the routes of MSG administration. J. Nutr. 102: 835-840,

Methylmalonate, Formiminoglutamate and Aminoimidazolecarboxamide Excretion of Vitamin B12-deficient Germfree and Conventional Rats

In order to evaluate the net influence of microbial metabolism on vitamin B12 nutriture, growth and urinary methylmalonic acid (MMA), aminoimidazolecarboxamide (AIC) and formiminoglutamic acid (FIGLU) were measured in male germfree and conventional rats fed a low methionine diet with or without vitamin B12 and during dietary supplementation with 1% of DL-methionine. Growth was retarded significantly among vitamin B12-deficient rats of both environments in comparison with their respective vitamin B12-supplemented controls. MMA excretion rose to 20 times the control level in conventional deficient rats but was only slightly elevated among germfree deficient animals. Though less dramatic, the same trend was true of AIC excretion. FIGLU excretion was elevated significantly in deficient animals of both environments. Methionine ingestion further enhanced MMA excretion of conventional deficient rats, suggesting that it served as a metabolic precursor. AIC excretion was unaffected by methionine feeding in contradiction to an earlier report. FIGLU excretion was depressed by DL-methionine supplementation to a greater extent among conventional than among germfree rats, perhaps indicating poor utilization of the D-isomer by germfree animals. These results show that MMA excretion is an unreliable index of vitamin B12 deficiency in the absence of conventional microbial metabolism and that the vitamin B12 requirement may be reduced in the germfree state.

Urinary organic acids found in B6-deficient rats and calcium oxalate calculus patients.

1 B6-deficient rats and calcium oxalate stone-forming patients share several metabolic abnormalities. 2 In our experiments, evidence for folic acid deficiency in the stone patients is strong, and some evidence exists in B6–deficient rats as well. 3 Susceptibility to overload of the acetyl coenzyme A system is high in both. 4 Sources of oxalic acid probably include aromatic amino acid derivatives with a 3 carbon side chain, whose metabolism is blocked by tyrosine, and whose dependence on the acetyl coenzyme A system is shown by the simultaneous drop in oxalate, hippurate, α-ketoglutarate and citric acids. That hydroxy-proline is a major source seems a probable explanation for changes in oxalate excretion with stress. 5 Both B6–deficient rats and hyperoxaluric patients respond to tyrosine administration by a drop in urinary oxalate.

Cholesterol metabolism and vitamin B 6 . IV. Synthesis of cholic acid conjugates in vitamin B 6 -deficient rats.

The in vitro conjugation of labelled free cholic acid with glycine and taurine in the livers of vitamin B6-deficient and pair-fed rats has been investigated. It appears from these results that vitamin B6-deficiency stimulates this conjugation, and some evidence is given which suggests that vitamin B6 may be responsible for the lower capacity of conjugation observed in the liver of the pair-fed rat.

Metabolic effects of propionate in normal and vitamin B 12 -deficient rats.

1. Administration of propionate caused a twofold increase in the concentrations of lactate and pyruvate in the blood of vitamin B(12)-deficient rats, whereas there was a slight decrease in lactate and a 50% increase in pyruvate in normal rats. 2. Concentrations of total ketone bodies in the blood of normal rats were not significantly altered by propionate administration but the [3-hydroxybutyrate]/[acetoacetate] ratio decreased from 3.0 to 2.0. In the vitamin B(12)-deficient rats there was a 40% decrease in total ketone bodies and a change in the ratio from 3.4 to 1.2. 3. The changes in the concentration of ketone bodies in freeze-clamped liver preparations were similar in pattern to those observed in blood. 4. Propionate administration caused a decrease in the concentration of acetyl-CoA in the livers of both groups of animals, but the absolute decrease was greater in the vitamin B(12)-deficient group. The decrease in the concentration of CoA was similar in both groups. 5. As in blood, there were threefold increases in the concentrations of lactate and pyruvate in the livers of the vitamin B(12)-deficient rats after propionate administration, whereas there was no significant change in the concentrations of these metabolites in the normal rats. 6. There was a 50% inhibition of glucose synthesis in perfused livers from vitamin B(12)-deficient rats when lactate and propionate were substrates as compared with lactate alone. 7. It is concluded that the conversion of lactate into glucose is inhibited in vitamin B(12)-deficient rats after propionate administration, and that this effect is due to inhibition of the pyruvate carboxylase step resulting from a decrease in acetyl-CoA concentration and a postulated increase in methylmalonyl-CoA concentration.

Homocystinuria: Observations on the Biosynthesis of Cystathionine and Homolanthionine

Extract: Patients with homocystinuria and a normal subject excreted cystathionine (1.8–15.0 μmoles/hr) after oral administration of homoserine plus cysteine; administration of both precursors is necessary. Excretion in the urine of the next higher homologue of cystathionine, homolanthionine, was found to occur spontaneously (0.8–1.5 μmoles/hr), but not constantly, in three of seven patients with homocystinuria; loading with homoserine increased homolanthioninuria (2.9–5.7 μmoles/hr). Optimum conditions were established in crude extracts of rat liver for in vitro synthesis of cystathionine from homoserine and cysteine (reverse cystathionase) and of homolanthionine from homoserine and homocysteine. Under these conditions, a greater capacity for synthesis of cystathionine by reverse cystathionase (1856 mμmoles/mg protein/hr \pm 95) than for its cleavage in the forward direction (951 mμmoles/mg protein/hr \pm 26) was demonstrated in liver; brain showed barely measurable activity in either direction. In crude extracts of livers from two patients with homocystinuria, activity of reverse cystathionase (39 and 56 mμmoles/mg protein/hr) was less than cleavage (144 and 396 mμmoles/nig protein hr), and both activities were far less than that found in rat liver extracts under the same conditions. Homolanthionine synthesis in rat brain was almost nil; in the other rat organs, it was far less than cystathionine synthesis by reverse cystathionase (compare 69 mμMoles/mg protein/hr \pm 2 in rat liver); it was greater in extracts of rat liver than in extracts of human liver (6.7–10.8 mμmoles/mg protein/hr in human liver); it was virtually absent from the liver of the vitamin B6-deficient rat, but activity was restored by pyridoxal phosphate added in vitro. Homolanthionine synthesis activity in rat liver was separated from cystathionine synthase by ammonium sulfate fractionation (Table IX); it was not separated from cystathionase by such fractionation or by chromatography on carboxymethylcellulose (Fig. 3). Speculation: Although administration of homoserine and cysteine results in urinary excretion of cystathionine by both normal subjects and those with homocystinuria, it is improbable that this treatment would promote the formation of any considerable amount of cystathionine in the brain, since evidence from rat studies indicates that the necessary

Effect of vitamin B6 deficiency on the metabolism of isolated fat cells: response to insulin, epinephrine and theophylline.

SummaryWhen isolated epididymal fat cells from vitamin B6-deficient rats were incubated with glucose, lipogenesis was greater both in the absence and presence of insulin than when fat cells from fed and fasted control animals were similarly treated. Fat cells from vitamin B6-deficient rats also appeared more sensitive to lipolysis induced by theophylline and to a lesser extent epinephrine. This effect appeared to be related at least in part to the inanition accompanying the vitamin deficiency. Insulin was effective in partially inhibiting the epinephrine effect on fat cells from ad libitum contols but not on fat cells from deficient rats or pair fed controls. Conversely, insulin appeared less effective in inhibiting the theophylline effect on fat cells from ad libitum controls than the other groups. Ratios of triglyceride to DNA were similar in fat cells obtained from control and deficient rats indicating that in rat vitamin B6-deficiency experiments the amount of fat cells used can be quantified by the a...

Effect of Vitamin B6 Deficiency on Tissue Dehydrogenases and Fat Synthesis in Rats

The activities of glutamate (GDH), lactate (LDH), isocitrate (ICDH), malate (MDH), and glucose-6-phosphate (G6PDH) dehydrogenases were measured in liver, adipose tissue, and renal cortex and medulla homogenates from control and vitamin B6-deficient rats. G6PDH and LDH were significantly decreased in liver homogenates from deficient animals when compared to both ad libitum and pair-fed controls. Significant increases in all five enzymes were seen in adipose tissue homogenates from deficient rats only when compared to ad libitum controls. Except for an increase in kidney cortex G6PDH no significant changes were found in kidney enzymes of deficient rats. Insulin administration partially reversed the decreases in liver G6PDH and LDH activities. There were no significant differences in the ability of liver slices from fasted ad libitum-fed control and deficient rats to synthesize lipid from glucose or acetate. In fed animals synthesis of liver lipids from glucose but not acetate was significantly higher in slices from deficient rats. These data indicate that although carcass levels of fat are especially low in vitamin B6-deficient rats, their liver and adipose tissue may have a greater than normal capacity to synthesize fat when glucose is metabolically available in sufficient quantities.

Metabolic effects of propionate administration to normal and vitamin B12-deficient rats.

Research Article| January 01 1971 Metabolic effects of propionate administration to normal and vitamin B12-deficient rats D L Williams; D L Williams Search for other works by this author on: This Site PubMed Google Scholar G H Spray; G H Spray Search for other works by this author on: This Site PubMed Google Scholar D H Williamson D H Williamson Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1971) 121 (1): 16P–17P. https://doi.org/10.1042/bj1210016Pb Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Cite Icon Cite Get Permissions Citation D L Williams, G H Spray, D H Williamson; Metabolic effects of propionate administration to normal and vitamin B12-deficient rats. Biochem J 1 January 1971; 121 (1): 16P–17P. doi: https://doi.org/10.1042/bj1210016Pb Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1971 The Biochemical Society1971 Article PDF first page preview Close Modal You do not currently have access to this content.

Urinary Methylmalonate and Hepatic Methylmalonyl Coenzyme A Mutase Activity in the Vitamin B12-deficient Rat

The amount of methylmalonate (MMA) excreted in the urine by rats maintained on vitamin B12-deficient diets was found to be a useful indicator of the severity of B12 deficiency. MMA was determined quantitatively by a new method as its ammonium salt, after separation from an ether extract of urine by one-dimensional paper chromatography. The extent of vitamin B12 deficiency in the liver was estimated by measuring the activity of methylmalonyl coenzyme A (MMCoA) mutase, decreased in the deficient state owing to depletion of the vitamin B12 coenzyme required for its function. In rats fed B12-deficient diets containing propionate, urinary MMA excretion > 1.5 μmoles per gram body weight per 24 hours reflected a decrease in hepatic MMCoA mutase activity to about 50% (or less) of the vitamin B12-supplemented control value. To simplify measurement of MMA, a rapid, semiquantitative screening test, detecting as little as 50 nmoles (about 6 μg) of MMA, was devised. The test can be done directly on filtered rat urine, without prior extraction, and provides a practicable method for evaluating the degree of vitamin B12 deficiency in the intact rat.

The effect of antibiotics on rats receiving a vitamin B12-deficient diet.

1. Rats fed on a vitamin B12-deficient or -supplemented diet were given either neomycin or a mixture of streptomycin and erythromycin by mouth for between 7 and 15 d. The urinary excretion of methylmalonic acid and the levels of vitamin B12 in plasma and tissues and of acetic and propionic acids in caecal contents were measured.2. Both treatments caused prompt reduction of methylmalonate excretion in the deficient rats. This was apparently due to depression of the production of some precursor of methyl-malonic acid, probably propionate, rather than to an immediate effect on vitamin B12 nutrition.3. After withdrawal of the antibiotics, neomycin-treated vitamin B12-deficient rats appeared to become partly repleted in vitamin B12, but the change in the vitamin B12 status of those which had received streptomycin and erythromycin was much smaller.

The oxidation of 5-methyl-14C-tetrahydrofolate and histidine-2-14C to 14CO2 in vitamin B12-deficient rats.

SummaryWhen rats were fed a diet deficient in vitamin B12 and limiting in methionine, the 14CO2 production from L-histidine-2-14C was reduced in comparison with rats fed diets supplementd with vitamin B12 and/or methionine. In contrast, the production of 14CO2 from 5-14CH3-tetrahydrofolic acid was not altered by vitamin B12 deficiency or the level of dietary methionine. The Tmax for the oxidation of 5-14CH3-tetrahydrofolic acid to 14CO2 was delayed in vitamin B12 deficiency in comparison with normals, indicating that either an enzymatic reaction or transport into tissues becomes rate-limiting in the deficient state.

Gluconeogenesis from propionate in kidney and liver of the vitamin B12-deficient rat.

1. Kidney-cortex slices and the perfused livers of vitamin B(12)-deficient rats removed propionate from the incubation and perfusion media at 33 and 17% respectively of the rates found with tissues from rats receiving either a normal or a vitamin B(12)-supplemented diet. There was a corresponding fall in the rates of glucose synthesis from propionate in both tissues. 2. The addition of hydroxocobalamin or dimethylbenzimidazolylcobamide coenzyme to kidney-cortex slices from vitamin B(12)-deficient rats in vitro failed to restore the normal capacity for propionate metabolism. 3. Although the vitamin B(12)-deficient rat excretes measurable amounts of methylmalonate, no methylmalonate production could be detected (probably because of the low sensitivity of the method) when kidney-cortex slices or livers from deficient rats were incubated or perfused with propionate. 4. The addition of methylmalonate (5mm) to kidney-cortex slices from rats fed on a normal diet inhibited gluconeogenesis from propionate by 25%. 5. Methylmalonate formation is normally only a small fraction of the flux through methylmalonyl-CoA. This fraction increases in vitamin B(12)-deficient tissues (as shown by the urinary excretion of methylmalonate) presumably because the concentration of methylmalonyl-CoA rises as a result of low activity of methylmalonyl-CoA mutase (EC 5.4.99.2). Slow removal of methylmalonyl-CoA might depress propionate uptake owing to the reversibility of the steps leading to methylmalonyl-CoA formation.

Factors affecting formiminoglutamic acid excretion in vitamin B 12 deficiency.

1. Formiminoglutamic acid, a product of the catabolism of histidine, is excreted in abnormally large amounts in the urines of vitamin B(12)-deficient rats and of vitamin B(12)-deficient sheep; the excretion is reduced to negligible amounts after administration of vitamin B(12). 2. After administration of certain methyl donors to vitamin B(12)-deficient rats or sheep urinary excretion of formiminoglutamic acid is temporarily decreased. 3. Irrespective of the pteroylglutamic acid status of the animals neither vitamin B(12)-deficient rats nor vitamin B(12)-deficient sheep have the ability to deal efficiently with histidine. 4. In sheep, urinary excretion of formiminoglutamic acid is increased after administration of aminopterin; treatment with pteroylglutamic acid restores the ability of the animal to deal with the catabolic products of histidine. 5. The possible functions of vitamin B(12) and methionine in relieving a virtual deficiency of pteroylglutamic acid are discussed.

Production of Urinary Calculi in Vitamin B6-deficient Male, Female and Castrated Male Rats

Evidence has been obtained indicating that there is a sex effect on the formation of urinary calcium oxalate stones in vitamin B6-deficient rats. When weanling rats were fed the deficient diet for 7 weeks, the prevalence and size of apical incrustations were greater in male than female or castrated male rats. When young adult rats were fed the deficient diets for 3 months, urinary stone formation appeared greatest in castrated male rats and least in females. After 6 months on the deficient diet, calculus formation was more marked than at 3 months and the differences between groups disappeared. The data of these studies suggest that the requirement for vitamin B6 is greater in male rats than in the other groups as demonstrated by a higher mortality and more rapidly increased excretion of xanthurenic and oxalic acids. Evidence has also been obtained using growth rates and liver storage of vitamin B6 in weanling rats fed varying levels of the vitamin that females may require less of the vitamin than male rats.

Glycine Metabolism in Vitamin B6-deficient and Deoxypyridoxine-treated Rats

Further studies in support of previous work indicating that vitamin B6 deficiency and deoxypyridoxine alter the metabolism of glycine by rats have been conducted. Vitamin B6 deficiency resulted in significant elevation in the free glycine of rat liver, kidney, blood and muscle. This effect was not accentuated by deoxypyridoxine and was prevented in liver and kidney. When vitamin B6-deficient rats were injected with glycine-1-14C less 14CO2 was expired than by controls. Deoxypyridoxine neither reversed nor increased this effect. Rats receiving deoxyridoxine converted less labeled glycine, glyoxylate and glycolate to hippuric acid than vitamin B6-deficient rats not receiving the analogue. Liver and kidney homogenates from vitamin B6-deficient rats showed a decreased ability to oxidize glycine-1-14C to 14CO2. This did not occur in liver homogenates from rats fed deoxypyridoxine, although kidney homogenates from these rats acted similarly to those from vitamin B6-deficient animals not receiving deoxypyridoxine. The addition of pyridoxal-5-phosphate to liver homogenates increased glycine oxidation in the homogenates from control rats and from both experimental groups to levels which were not significantly different. In contrast, pyridoxal-5-phosphate did not alter the glycine oxidation of control kidney homogenates and did not raise the activity of kidney homogenates from the deficient groups to control levels.

Cellular Antibody Synthesis in Vitamin B6-deficient Rats

Cellular antibody synthesis was determined by the Jerne agar-plaque technique in normal and vitamin B6-deficient rats immunized with sheep erythrocytes. A severe reduction in the number of individual antibody-forming cells was observed in spleens from immunized deficient animals. This decreased cellular immune response was independent of the inanition associated with the deficiency and was restored to normal by the administration of pyridoxine shortly before immunization. Accumulation of antigen by rat spleen did not appear to be deranged in vitamin B6 deficiency.

Urinary Aminoimidazolecarboxamide in the Rat as Influenced by Dietary Vitamin B12, Methionine and Thyroid Powder

The objectives of this investigation were to 1) determine whether aminoimidazolecarboxamide (AIC), like formiminoglutamic acid, was elevated in the urine of rats fed a vitamin B12-methionine-deficient diet; 2) assess the value of thyroid powder supplementation in enhancing the development of vitamin B12 deficiency; and 3) study the effect of supplementary methionine on AIC excretion. Vitamin B12-supplemented controls averaged about 20 μg of urinary AIC/day. Rats fed the vitamin B12-deficient diet for 6 weeks or more excreted at least twice as much. Thyroid powder did not alter urinary AIC excretion, nor did it enlarge the difference in weight gain between vitamin B12-supplemented and deficient animals. Injection of 10 μg of vitamin B12 or supplementation of the diet with 2% of DL-methionine lowered AIC excretion of vitamin B12-deficient rats to the level of vitamin B12-supplemented controls, but had no effect on the AIC excretion of the control animals. The results of this investigation are consistent with the theory that vitamin B12 influences folic acid metabolism at the level of methionine biosynthesis.

Some Effects of Amino Acid Deficiencies on Antibody Formation in the Rat

The effects of a variety of nutritional deficiencies on antibody formation in rats have been studied. Deficiencies of vitamin B6, tryptophan and phenylalanine in rats decreased the antibody response to the synthetic antigen, poly Glu52Lys33Tyr15 (no. 3) or to the natural antigen, sheep red blood cells. Methionine deficiency, methionine excess, or caloric restriction did not alter the antibody response. The metabolic antagonist deoxypyridoxine further decreased the antibody response in vitamin B6-deficient rats. The effect was reversed partially by glycine or serine, serine being more effective on a molar basis. Ethionine, a methionine antagonist decreased the antibody response, and its effect was not reversed by adenine or by methionine. The antibody response in germfree rats was higher than in normal animals.

Effects of vitamin B6 and B1 deficiencies and restricted caloric intake on tissue zinc levels.

Studies from this laboratory have suggested that there is a decreased availability of insulin in vitamin B6 deficient rats (1). Although the role of zinc on insulin metabolism has never been determined, associations of zinc and insulin have been reported for more than 30 years. Recent in vitro studies (2,3) using isolated epididymal adipose tissue have clearly shown that zinc in concentrations in the range of those observed in human and rat plasma and higher inhibit insulin activity. Hsu (4) has reported that vitamin B6 deficiency in rats results in decreased zinc content of plasma, liver, pancreas, and heart tissues. Work in this laboratory using a different experimental protocol appeared in disagreement with Hsu's conclusions. This report contains a study of the effects of vitamin B6 deficiency on tissue zinc concentrations. Since some pyridoxal enzymes are magnesium dependent and it has been shown that magnesium supplementation of vitamin B6 deficient rations for rats prevents at least in part some effects of vitamin B6 deficiency, [protects against calcium oxalate urolithiasis, increases urinary citrate and decreases xanthurenic acid excretion (5)] the effects of vitamin B6 deficiency on tissue Mg levels were also investigated. To partially determine how specific the effects observed were, studies of the effects of thiamine deficiency and restricted feeding on zinc tissue levels and the effects of restricted feeding and vitamin B6 deficiency on potassium tissue levels were also under taken. Experimental. Weanling male Charles River CD rats were used in these studies. They were fed semipurified diets containing in percent: casein, 25; sucrose, 70.7; corn oil, 9; cod liver oil, 1; salts IV (6), 4; and choline, 0.3. Eight mg of riboflavin, 40 mg of niacin, 20 mg of calcium pantothenate, 1 mg of folic acid, 1 mg of menadione, 0.2 of biotin, 0.05 mg of vitamin B12 and when used 4 mg of thiamine hydrochloride, and 4 mg of pyridoxine hydrochloride were added to each kilogram of diet. The basal diet contained 40 mg of magnesium and 1.4 mg of zinc/100 gm.