Tissue Ascorbic Acid Concentrations Research Articles

Quantifying determinants of ozone detoxification by apoplastic ascorbate in peach (Prunus persica) leaves using a model of ozone transport and reaction.

Ascorbate in leaf apoplast (ASCapo ) reacts with ozone (O3 ) and thereby reduces O3 flux reaching plasmalemma (Fpl ). Some studies have shown significant protection of cells from O3 by ASCapo , while others have questioned its efficacy. Hypothesizing that the protection by ASCapo depends on other variables, we quantified determinants of O3 detoxification with a model of O3 transport and reaction in apoplast. The model determines ascorbic acid concentration in apoplast (AAapo ) using measured values of O3 concentration (co ), leaf tissue ascorbic acid concentration (AAleaf ), cell wall thickness (L3 ), apoplastic pH (pHapo ), and stomatal conductance (Gsw ). We compared the measured and model-estimated AAapo in leaves of peach (Prunus persica) grown in open-top chambers under non-filtered air (NF) and elevated (EO3 : NF+80ppb) O3 concentrations. The estimated AAapo in individual leaves agreed well with the measured values (R2 =.91). Analyses of the simulation results yielded the following findings: (a) The efficacy of O3 reduction with ASCapo as quantified by fractional reduction (ϕ3 ) of O3 flux at the surface of plasmalemma (Fpl ) was lowered from 70% in NF to 40% in EO3 due to the reduction of L3 . The EO3 reduced AAapo , but the lower Gsw and L3 in EO3 increased AAapo resulting in no significant change in AAapo due to EO3 . ϕ3 can be calculated with measured values of AAapo and L3 , and Fpl can be estimated with the measurement-based ϕ3 . (b) When c0 is increased, Fpl increased curvilinearly with the increase of Fst : nominal O3 flux via stomatal diffusion, exhibiting apparent threshold on Fst . The deviation of Fpl from Fst became greater when L3 , pHapo , and AAleaf were increased. The quantification of ϕ3 and Fpl using leaf traits shall facilitate the understanding of the mechanisms of differential plant sensitivity to O3 and improve quantification of the O3 impacts on plants.

The Effects of Dietary Vitamin C Levels on Tissue Ascorbic Acid Concentration and Growth in European Sea Bass (Dicentrarchus labrax, L.1758)

The effect of different dietary levels of L-ascorbic acid on the growth and vitamin C concentration in the tissue of European Sea bass (Dicentrarchus labrax, L.1753) with an initial body weight of 4.6±1.1 g was studied. Four practical diets were formulated to containing 10 (AA10), 25 (AA25), 42 (AA42) and 65 (AA65) mg ascorbic acid equivalent kg-1 diet. The results of a 20 week feeding trial showed that typical vitamin C-deficiency signs and high mortality in the fish fed with the AA10 diet. The fish fed with AA42 (42 mg kg-1 AA diet) showed a significantly higher final body weight than the other diets (P less than 0.05) and the concentrations of ascorbic acid (AA) in the brain of these fish were higher than in the other experimental group (P less than 0.05). In this study, the amount of storage in the organs occurred in this order: brain, kidney, liver.

Effects of dietary vitamin C levels on tissue ascorbic acid concentration, hematology, non-specific immune response and gonad histology in broodstock Japanese eel, Anguilla japonica

A feeding trial was conducted to evaluate the effects of dietary vitamin C (L-ascorbic acid, AA) levels on tissue AA concentration, hematology, non-specific immune response and gonad histology in male broodstock Japanese eel. A basal commercial diet was used as a control, and four other diets were prepared by supplementing 200, 400, 800 or 1600 mg AA kg − 1 diet in the form of L-ascorbyl-2-monophosphate (AMP). The analyzed AA concentrations of the diets were 32, 206, 423, 840 and 1686 mg kg − 1 diet, respectively. Triplicate groups of fish (initial body weight, 360 g) were fed one of the test diets at a ratio of 2% body weight for 16 weeks. At the end of the feeding trial, AA concentration in liver, kidney, muscle and testes was increased significantly in a dose dependent manner by increment of dietary AA level ( P < 0.05). Significantly higher hematocrit value was found in fish fed 1686 mg AA kg − 1 diet compared to 32 and 423 mg AA kg − 1 diets. White blood cells count of fish fed 1686 mg AA kg − 1 diet was significantly higher than those of fish fed 32–206 mg AA kg − 1 diet. Plasma glucose concentration was increased significantly with increasing dietary AA levels up to 840 mg AA kg − 1 diet; also significant enhancements in aspartate aminotransferase and alanine aminotransferase values were obtained at 1686 mg AA kg − 1 diet. Significantly higher superoxide dismutase activity was recorded in fish fed 840–1686 mg AA kg − 1 diet compared to 32–206 mg AA kg − 1 diet. The results of gonad histology showed an enhanced number of spermatogonia by dietary AA increment. The optimal dietary AA requirement level was estimated at approximately 410.8 and 911.8 mg AA kg − 1 diet by broken-line regression analysis based on liver and testes AA concentration, respectively. • Supplemental effect of vitamin C was investigated in diet for broodstock Japanese eel. • Dietary vitamin C supplementation augmented fish non-specific immune response. • Increment of dietary vitamin C level reduced lipid peroxidation. • Tissue vitamin C concentration reflected the dietary vitamin C levels. • Gonad histology showed the enhancement of collagen synthesis by vitamin C increment.

Effect of high-dose vitamin C supplementation on growth, tissue ascorbic acid concentrations and physiological response to transportation stress in juvenile silver pomfret, Pampus argenteus

Summary This study investigated the effect of high-dose vitamin C supplementation on growth, tissue ascorbic acid concentrations and physiological response to transportation stress in juvenile silver pomfret, Pampus argenteus (initial average weight 6.2 ± 0.2 g). Three practical diets were formulated to contain 100 (control), 450 and 800 mg ascorbic acid/kg diet, respectively, supplied as l-ascorbyl-2-polyphosphate. Each diet was fed to triplicate groups of fish in circular tanks (3 m o, 1.5 m depth) (60 fish/tank) for 9 weeks. Growth did not change significantly with dietary vitamin C levels, although an improvement tendency with an increase in vitamin C supplementation was observed. Ascorbic acid concentrations in the liver and muscle of fish fed diets containing graded levels of vitamin C were positively correlated with dietary levels of this vitamin. Tissue ascorbic acid concentrations significantly increased with increasing vitamin C supplementation. After 9 weeks, the fish were subjected to transportation stress for 4 h to determine the influence of high vitamin C supplementation on the physiological response to this stressor. Serum cortisol, glucose and lactate levels significantly increased in stressed fish. Serum cortisol and glucose concentrations after stress were significantly higher in fish fed the control diet (7.91 μg L−1 and 0.80 mm, respectively) than in the other groups. However, there were no significant differences in serum cortisol and glucose levels after stress between the 450 and 800 mg kg−1 diets. No significant change could be found in serum lactate levels after stress among the different treatments. In conclusion, the dietary administration of high doses of vitamin C could reduce stress in silver pomfret and increase the survival of fish under stress conditions.

Dietary ascorbic acid requirement of cobia, Rachycentron canadum Linneaus

A 10-week feeding trial was conducted to determine the optimal requirement of cobia (Rachycentron canadum Linneaus) for dietary ascorbic acid (AA). Graded levels of L-ascorbyl-2-polyphosphate (LAPP) were supplemented in basal diet to formulate six semi-purified diets containing 2.70 (the control diet), 8.47, 28.3, 80.6, 241 and 733 mg AA equivalent kg−1 diet, respectively. Each diet was randomly fed to triplicate groups of fish in flow-through plastic tanks (300 L), and each tank was stocked with 25 fish with average initial weight of 4.59 ± 0.36 g. Observed deficiency signs included poor growth, higher mortality and lower feeding rate (FR) in the fish of the control group. Fish fed the control diet had significantly lower weight gain (WG), lower feed efficiency ratio (FER) and lower tissue AA concentrations in fish liver and muscle. With the increase of dietary AA, the survival, WG, FER, hepatic and muscular AA concentrations of cobia significantly increased and then levelled off. The dietary AA requirement of cobia was estimated to be 44.7 mg kg−1 based on WG, 53.9 mg kg−1 or 104 mg kg−1 based on either hepatic or muscular AA concentration, respectively.

Restoration of Vitamin C Synthesis in Transgenic Gulo−/− Mice by Helper-Dependent Adenovirus-Based Expression of Gulonolactone Oxidase

Inability to synthesize vitamin C, because of a deficiency in gulonolactone oxidase (GULO) expression, is a genetic deficiency shared by a small number of animals including humans. Although the most overt symptom of vitamin C deficiency, scurvy, can be readily corrected by modest consumption of vitamin C, there is increasing interest in the effect of high-level administration in treating human disease. Using a previously derived Gulo-expressing vector, which produces murine GULO under the control of the murine cytomegalovirus (mCMV) promoter, we constructed and validated a recombinant helper-dependent adenovirus (HDAd-mCMV-Gulo) that can be used to correct this genetic defect. A human liver cell line (Hep G2) infected with the HDAd-mCMV-Gulo vector expressed GULO in a time- and gene dose-dependent manner. These cells also produced ascorbic acid when exogenous gulonolactone was supplemented in the medium. Likewise, Gulo(-/-) mice treated with HDAd-mCMV-Gulo at 2 x 10(11) VP expressed GULO in the liver and produced ascorbic acid. Serum ascorbic acid concentrations in Gulo(-/-) mice injected with GULO-expressing HDAd were elevated to levels comparable to those of wild-type mice (62 +/- 15 microM) after 4 days of infection and were maintained at significantly higher levels compared with those in untreated Gulo(-/-) mice for at least 23 days. A similar elevation was observed in urine and tissue ascorbic acid concentrations in vector-treated animals. In conclusion, we demonstrate here that gene therapeutic HDAd-mCMV-Gulo vectors can mediate the expression of GULO and endogenous production of ascorbic acid in human cells and in Gulo(-/-) transgenic mice. Taken together, these data show that a gene therapy approach can be successfully employed in the treatment and further study of vitamin C deficiency in scurvy-prone mammals.

Sexual difference in ascorbic acid synthesis, tissue ascorbic acid and plasma total antioxidant capacity in mature chickens

1. An experiment was conducted with commercial White Leghorn type chickens to determine the effect of gender on tissue ascorbic acid concentration, antioxidant capacity and ascorbic acid synthesis. 2. Birds reared and maintained on litter were given a standard layer diet, without supplemental ascorbic acid, from 18 weeks of age. Tissue ascorbic acid concentration, plasma total antioxidant capacity and renal L-gulonolactone oxidase activity were measured at 30 weeks of age. 3. Females and males differed in ascorbic acid synthesis, as measured by renal L-gulonolactone oxidase activity, and tissue ascorbic acid concentration. 4. Plasma total antioxidant capacity and adrenal, gonadal, plasma and pituitary ascorbic acid concentrations were significantly higher in males, whereas ascorbic acid synthesis and splenic and thymic ascorbic acid concentrations were significantly higher in females. 5. L-Gulonolactone oxidase activity was not detected in the comb of cockerels.

Effect of chronic oxidative/corticosterone‐induced stress on ascorbic acid metabolism and total antioxidant capacity in chickens (Gallus gallus domesticus)

The consequences of chronic corticosterone-induced stress (CCIS) on ascorbic acid (AsA) metabolism in chickens, an animal that syntheses the vitamin, are not known. This study was conducted to determine whether CCIS alters AsA synthesis, as measured by l-gulonolactone oxidase (GLO) activity, tissue AsA, lipid peroxides and tissue total antioxidant capacity (TAC). Stress was induced by dietary administration of corticosterone from 2 to 4 weeks of age and measurements were made at 0, 7 and 14 days post-treatment. Ascorbic acid synthesis was not influenced by CCIS but hepatic, cardiac, renal, bursal and duodenal AsA concentrations were significantly decreased and plasma TAC and uric acid concentrations were significantly elevated. Stress caused significant hepatomegaly and hepatic lipidosis but hepatic peroxides were not elevated despite the slight decrease in hepatic TAC. Tissue TAC varied in different organs. It was markedly elevated in the kidney, reduced by 49% in the spleen, and changes were not detected in the heart and duodenum even though AsA concentration was significantly decreased in all tissues. We conclude that CCIS caused a significant reduction in tissue AsA concentration but did not inhibit GLO activity. The change in AsA concentration was associated with increase, decrease or no change in TAC in tissues examined. The findings suggest that CCIS may alter AsA recycling, influx or turnover in different tissues of chickens.

α-Lipoic acid-enrichment partially reverses tissue ascorbic acid depletion in pacu (Piaractus mesopotamicus) fed vitamin C-devoid diets

Effects of dietary α-lipoic acid (LA) and ascorbic acid (AA) on the growth, tissue vitamin C and tocopherol (vitamin E) levels, and malondialdehyde levels were examined in the tropical fish pacu, Piaractus mesopotamicus. Pacu juveniles were fed one of four casein-gelatin-based diets for 8 weeks: with 0.05% AA and 0.1% LA (+AA+LA), with AA and without LA (+AA–LA), without AA and with LA (−AA+LA), and without AA and LA (−AA−LA). When the fish received quantities of feed equal to 1.9–2.5% of its body weight, growth was not influenced, regardless of the presence of AA or LA throughout most of the experimental period. Growth was, however, slightly but significantly lower at week 8 in the AA-deficient/LA-supplemented group. An AA-deficient diet caused a highly significant reduction in both total AA and dehydroascorbic acid content in the liver and gill tissues. This reduction of tissue AA concentrations was reversed in a significant manner by LA (antioxidant-sparing effect). The 8-week-long vitamin C deprivation was sufficient to initiate the reduction in tissue ascorbic acid; however, total ascorbate in the liver of fish in the (−)AA/(+)LA group was 127.7±54.3 nmol g−1 tissue, whereas it was 28.6±26.3 nmol g−1 in the (−)AA/(−)LA group, a 4.4-fold difference. This mitigating effect of the addition of the endogenous antioxidant LA to the diet indicates that LA exerts a vitamin C-sparing effect in teleost fish that by far exceeds the phenomena demonstrated in non-scurvy-prone mammals. There was no difference among the different diet groups for vitamin E and malondialdehyde levels in the liver. These results suggest that LA is a potent substance for the prevention of AA deficiency in cultured fishes. The optimal dietary level of LA needs to be determined in the light of the slight reduction in body weight gain after 8 weeks of feeding in the absence of AA.

Ascorbic acid biosynthesis in hens producing strong and weak eggshells

1. An experiment was conducted with two strains of layers to ascertain whether the reduction in eggshell strength occurring at the end of the production cycle is the result of reduced ascorbic acid biosynthesis. 2. Hens producing strong and weak eggshells were identified within each strain and egg production, egg weight, per cent shell, shell surface density, plasma, adrenal and hepatic ascorbic acid and renal L-gulonolactone oxidase activity were measured. 3. The strains differed in ascorbic acid synthesis, as measured by L-gulonolactone oxidase activity, and tissue ascorbic acid concentration. 4. Comparison of results from birds producing eggs of similar weight but markedly different in shell strength detected neither a shell strength group × strain interaction nor an effect of shell strength group on plasma and hepatic ascorbic acid and activity of L-gulonolactone oxidase. 5. The results did not support the hypothesis that tissue ascorbate and ascorbic acid biosynthesis are reduced in old hens producing weak eggshells.

Comparison of l-ascorbyl-2-monophosphate-Ca with l-ascorbyl-2-monophosphate-Na/Ca on growth and tissue ascorbic acid concentrations in Korean rockfish ( Sebastes schlegeli)

This experiment was conducted to compare l-ascorbyl-2-monophosphate-Ca (AMP-Ca) with l-ascorbyl-2-monophosphate-Na/Ca (AMP-Na/Ca) for supplying the dietary vitamin C for juvenile Korean rockfish ( Sebastes schlegeli). Fish were fed 1 of 11 semi-purified diets containing equivalent of 0, 50, 100, 200, 400, and 800 mg ascorbic acid (AA)/kg diet in the form of AMP-Ca or AMP-Na/Ca for 12 weeks. After 12 weeks of the feeding trial, weight gain (WG), feed efficiency (FE) of fish fed with the control diet (vitamin C-deficient diet) were significantly lower than those of fish fed with the vitamin C-supplemented diets in either form ( P<0.05). WG of fish fed with AMP-Na/Ca 400, AMP-Na/Ca 800, AMP-Ca 400 and AMP-Ca 800 diets were significantly higher than those of fish fed with the control diet, AMP-Na/Ca 50, AMP-Ca 50 and AMP-Ca 100 diets ( P<0.05). In general, there was no significant difference between AMP-Ca diets and AMP-Na/Ca diets at the same supplementation levels. By the end of the 9th week, fish fed with the control diet began to show the initial vitamin C deficiency signs such as anorexia, erratic swimming behavior, darkening in skin color and reduced growth. The ascorbic acid concentrations in fish muscle and liver increased with the increase of the vitamin C supplementation levels in fish diets regardless of which kind of vitamin C source used. There were no significant differences in ascorbic acid concentrations in liver and muscle of fish between the two vitamin C sources at the same supplementation level. These results indicate that AMP-Ca is a bioavailable form of vitamin C source for Korean rockfish and it has the antiscorbutic activity equal to AMP-Na/Ca. Broken-line analysis of weight gain indicated that the dietary vitamin C requirement of Korean rockfish was 106 mg AA/kg diet based on the pooled WG of fish fed with the AMP-Na/Ca and AMP-Ca diets. However, based on the different forms of ascorbic acid, the vitamin C requirements were 101 and 112 mg AA/kg diet with the forms of AMP-Na/Ca and AMP-Ca, respectively.

Factors affecting ascorbic acid biosynthesis in chickens: III. Effect of dietary fluoride on L-gulonolactone oxidase activity and tissue ascorbic acid (AsA) concentration.

The inconsistent beneficial responses to dietary ascorbic acid (AsA) may be due to dietary factors that alter biosynthesis or tissue turnover of AsA. It has been suggested on the basis of altered tissue AsA that dietary fluoride is a determinant of biosynthesis in chickens. Fluoride may enter the food chain of poultry via industrial contamination, feed ingredients and drinking water. The goal of this study was to ascertain whether dietary fluoride at 300 mg/kg influences l-gulonolactone oxidase (GLO) activity in commercial meat-type chickens. The experimental diet was fed from day-old to 3 weeks and responses measured. Growth and feed conversion were not affected by fluoride in the diet. Dietary fluoride neither inhibited nor enhanced GLO activity nor did it increase or decrease AsA concentration in plasma, liver, kidney, adrenal gland and muscle (pectoralis major). Tissue AsA concentration in ascending order was adrenal > liver > kidney > pectoralis major > plasma. The results are consistent with that reported for the rat and calculations based on the results eliminate fluorine contamination for the inconsistent responses of immature chickens to dietary AsA.

Effects of the different levels of dietary vitamin C on growth and tissue ascorbic acid changes in parrot fish ( Oplegnathus fasciatus)

An 11-week feeding trial was conducted to study the effects of the different levels of dietary vitamin C on growth, tissue ascorbic acid concentrations and histopathological changes in parrot fish. Casein and gelatin-based diets were formulated to contain 0, 60, 120, 240, 480 and 2000 mg l-ascorbic acid (AA) per kg diets on AA equivalent basis in the form of l-ascorbyl-2-monophosphate (AMP), 60 and 240 mg AA per kg diet as l-ascorbic acid. However, the analyzed AA levels were 0, 50, 100, 205, 426 and 1869 mg AA per kg diet in AMP supplemented diets; 36 and 149 mg AA per kg diet in l-ascorbic acid supplemented diets. Thus, the diets were designated as AA-free, AMP 50, AMP 100, AMP 205, AMP 426, AMP 1869, AA 36 and AA 149. Fish averaging 3.9±0.06 g (mean±S.D.) randomly were fed the experimental diets in triplicate groups for 11 weeks. Weight gain (WG) of fish fed AMP 50 and AA 36 diets were significantly lower than those of the other groups, and fish fed AMP 1869 diet showed a higher WG than did fish fed AMP 50, AMP 100, AMP 205, AA 36 and AA 149 diets ( P<0.05). However, there was no significant difference in WG between fish fed diets AMP 426 and AMP 1869, and among fish fed AMP 100, AMP 205, AMP 426 and AA 149 diets. Fish fed the AA-free diet began to show deficiency signs, such as retarded growth, darkening, anorexia and high mortality, after 3 weeks of feeding trial. After 6 weeks of the feeding trial, liver from fish fed the AA-free diet showed severe atrophy. By the end of the seventh week, all fish fed the AA-free diet were dead. Liver AA concentration from fish fed AMP 50 diet was significantly lower than that from fish fed AMP 205, AMP 426, AMP 1869 and AA 149 diets, and fish fed AMP 50, AMP 100, AA 36 diets showed a significant lower AA concentration in liver than did fish fed AMP 205, AMP 426 and AMP 1869 diets. Broken line analysis of weight gain indicated that the dietary vitamin C requirement of parrot fish is 118±12 mg AA per kg diet in the form of l-ascorbyl-2-monophosphate for maximum growth.

Liver L-Gulonolactone Oxidase Activity and Tissue Ascorbic Acid Concentrations in Nursing Pigs and the Effect of Various Weaning Ages

In Experiment 1, we evaluated liver L-gulono-gamma-lactone oxidase (GLO) activity and tissue concentration of ascorbic acid in young pigs from birth to weaning (14 d) and through a 28-d postweaning period; in Experiment 2, we evaluated the effect of three weaning ages on these measurements. Sow colostrum and milk collected in both experiments demonstrated a linear decline (P < 0.01) in ascorbic acid concentration as lactation progressed. In Experiment 1, three pigs were killed at 0, 3, 7, 14, 21, 28, 35 and 42 d of age for determining liver GLO activity and serum and tissue ascorbic acid. Liver GLO activity decreased by 80% from 0 to 3 d of age and remained low until d 14 (weaning). After weaning, liver GLO activity increased linearly (P < 0.01). Tissue ascorbic acid concentrations decreased during the nursing period and again after weaning, but then increased to 42 d of age (P < 0.01). In Experiment 2, pigs were weaned at 10, 17 or 24 d of age. Three pigs from each group were killed at weaning and at each week postweaning until 38 d of age. Liver GLO activity was low during the nursing period but increased linearly (P < 0.01) for each group during the subsequent postweaning period. Pig serum and tissue ascorbic acid concentrations increased postweaning in each group. These results suggest that a factor in sow's milk, possibly ascorbic acid, suppressed liver GLO activity of nursing pigs but upon weaning, liver GLO activity of pigs increased in a linear manner (P < 0.01).

O3-induced inflammation in prepregnant, pregnant, and lactating rats correlates with O3 dose estimated by18O

Previous studies have shown that rats late in pregnancy and throughout lactation are more susceptible to ozone (O3)-induced pulmonary inflammation than are prepregnant (virgin) or postlactating rats. The major aim of the present study was to determine whether these differences in response intensity could be accounted for by the O3 dose to the lower region of the lung. The relative O3 dose to the lower lung of groups of pregnant, lactating, and virgin female rats was estimated by measuring the incorporation of the 18O isotope into low-speed (cells) and high-speed (surfactant) pellets of bronchoalveolar lavage fluid immediately after acute exposure to 0.5-1.1 parts/million 18O3. The polymorphonuclear leukocyte (PMN) and protein inflammatory responses were established 20 h after acute exposure of identical physiological groups to 0.5-1.1 parts/million 16O3 (common isotope). A single regression of PMN inflammation data against surfactant 18O concentration for all physiological groups gave a linear relationship, indicating direct proportionality of PMN inflammation with this estimate of relative dose to the lower lung regardless of physiological status. This implies that the chemical species that react with surfactant molecules, i.e., O3 or its metabolites, are the same as or proportional to those chemical species responsible for initiating PMN inflammation. Additional experiments showed that lung tissue ascorbic acid concentration was significantly lower in pregnant and lactating rats than in virgin female rats. Although a causative relationship cannot be assumed, the deficit in tissue ascorbic acid concentration in pregnant and lactating rats compared with virgin female rats is consistent with their greater responsiveness and higher relative surfactant O3 dose.

Comparative studies on the nutrition of two species of abalone, Haliotis tuberculata L. and Haliotis discus hannai Ino. : VII. Effects of dietary vitamin C on survival, growth and tissue concentration of ascorbic acid

The experiment was conducted to investigate the effects of dietary vitamin C on survival, growth and tissue ascorbic acid (AsA) concentration of abalone, Haliotis tuberculata and H. discus hannai. Eight purified diets were formulated to provide a series of graded levels of vitamin C (0–800 mg/100 g diet) from either supplemental crystalline AsA (1 level) or AsA coated with hydrogenated vegetable oil (7 levels). The red alga, Palmaria palmata, was used as a control diet. Abalone juveniles of similar size were distributed in a recirculating system using a completely randomized design with 9 treatments and 3 replicates per treatment. They were fed the appropriate diet every 3rd day for a 100-day period. Survival and growth of both abalone species were not significantly affected by the dietary treatments ( P>0.05); and no deficiency signs were observed. Tissue AsA concentration, however, increased with the increase in dietary AsA. Abalone fed the diet containing crystalline AsA (200 mg/100 g) had significantly lower levels of carcass AsA than those fed the ascorbate-free diet. P. palmata resulted in a similar (in H. tuberculata) or a higher (in H. discus hannai) tissue AsA level than the purified diet with the highest level of coated AsA. H. tuberculata had a significantly higher mean level of tissue AsA than H. discus hannai.

Bioavailability of vitamin C from two ascorbyl monophosphate esters in rainbow trout, Oncorhynchus mykiss (Walbaum)

The relative bioavailability of ascorbic acid (AA) from several sources was compared in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum). Fingerling trout were offered AA, and equimolar amounts of ascorbyl monophosphate Ca salt (CaAMP) or ascorbyl monophosphate-K, Mg salt (K/MgAMP) at graded levels of 20, 40, 80 and 320 mg kg−1. A control group was fed the same formula diet devoid of AA. During the 12 week long experiment, dietary concentrations of CaAMP and K/MgAMP remained unchanged while AA concentration decreased by 62.5%. No significant growth differences were found over a 12 week growout period, during which body weights increased 8–9 fold. No mortality or acute scurvy signs were observed in fish. Lysozyme activities tended to decrease in fingerlings supplemented with the highest AA level from all sources, although the difference was significant only in the case of the CaAMP diets. Blood plasma alkaline phosphatase showed no significant differences between treatments. However, phosphatase activity toward ascorbyl monophosphate (AMP) extracted from the intestine showed a gradual increase as the dietary AMP source was increased from 20 to 80 mg kg−1. Significant differences were found in AA concentration in the liver after 3 weeks of feeding graded levels of different sources of ascorbic acid. The differences in tissue AA concentrations among groups fed different dietary supplements increased with the duration of feeding. The bioavailability of AA and AA esters as measured by AA concentrations in the liver, kidney, intestine and blood plasma were equal. Despite the decrease in AA concentration in feeds supplemented with unprotected ascorbic acid after several weeks of storage, relationships between concentrations of ascorbic acid in the liver and those actually measured in feeds were not significantly different between treatments.

Copper status and ascorbic acid concentrations in rats

Copper is a trace element essential for several biological systems. Important cuproenzymes, peptidylglycine α-amidating monooxygenase (PAM) and dopamine-β—monooxygenase (DBM), also require ascorbic acid (AA) as a cosubstrate for normal activity. To extend previous studies in mice, AA was determined in organs from thirty-day-old copper-adequate (+Cu) and copper-deficient (-Cu) male and female rats. Copper deficiency was initiated during the last two weeks of gestation and verified by the severe reduction in liver and brain copper concentrations, 85 and 75% respectively. Rat tissue AA concentrations were determined by HPLC with electrochemical detection. Brain, liver, and kidney were not influenced by diet while spleens from -Cu rats contained 20% less AA than controls. In a second study, male weanling rats were fed a -Cu diet for 5.5 weeks and compared to +Cu controls. Sixty-day-old male rats, +Cu and -Cu, had comparable AA levels but differing Cu status. Changes in PAM and DBM activity in -Cu rats are not likely to be influenced by changes in AA. Brain cortex and cerebellum AA levels were determined between birth and 6-weeks of age in control rats. A marked rise in cerebellar AA was noted during lactation which fell upon weaning.

Exercise and tissue ascorbic acid content in guinea pigs

The effects of treadmill exercise (20 m/min, five days/wk, one hr/day) on growth and tissue ascorbic acid (AA) concentrations were investigated in 40 young, male guinea pigs. Animals were fed ad libitium an AA-free diet which was supplemented with AA. AA was administered daily via gavage feeding. Animals were divided into two groups, exercise (E) and sedentary (S). Food consumption and body weight were recorded. After eight weeks, animals were sacrificed and blood taken via heart puncture. Liver, spleen, adrenals and kidneys were removed, weighed and frozen. Plasma and organ tissues were analyzed for AA. Results indicated that exercise had no significant effect on growth. Growth was within normal range. Exercised animals had significantly (p<0.05) lower AA concentrations in liver (E, 3.29±0.63; S, 3.73±0.58 mg/100 g, mean±SD) and adrenal (E, 18.06±5.41; S, 21.98±7.88 mg/100 g) tissue as compared with sedentary guinea pigs. In summary, moderate running significantly reduced the AA concentration of liver and adrenal glands. These results suggest that AA requirement may be increased with moderate exercise.

Effect of increasing storage iron on ascorbic acid metabolism in the guinea pig

Ascorbic acid (AA) metabolism was studied in control and iron-loaded guinea pigs. All animals were fed an AA-deficient diet and given a daily intraperitoneal (ip) dose of 10 mg sodium ascorbate. The control-diet formula contained 0.10 g Fe/kg diet; the experimental diet contained an additional 3.33 g Fe/kg diet as FeSO4. After 14 wk animals were injected (ip) with 9.25 x 10(3) Bq [1-14C]L-ascorbic acid. Blood was collected for 10 d and plasma specific activity of AA was determined. All animals were subsequently killed and selected tissues were analyzed for AA and iron concentrations. In spite of marked elevation of iron concentrations in plasma, spleen, and liver in experimental animals compared with controls, no differences in AA metabolism as determined by tissue AA concentrations and AA half-life, turnover rate, and body-pool size were evident. These results demonstrate that iron loading has no effect on the rate of AA catabolism in guinea pigs.