Reactions of hypothalamic ascorbic acid, serum ceruloplasmin and the adenohypophysis to oestradiol: inhibition by L-thyroxine

Four weeks' administration of oestradiol benzoate to male and female rats in doses of 1 mg twice a week leads to adenohypophyseal hyperplasia and to an increase in the thyroxine-binding capacity of the adenohypophyseal proteins in vitro. At the same time, serum polyphenol oxidase (ceruloplasmin) activity rises and the hypothalamic ascorbic acid concentration falls. The simultaneous administration of L-thyroxine (0.1 mg/rat/per day) or dried thyroid (but not D-thyroxine) significantly inhibits these changes (adenohypophysis, ceruloplasmin) or completely suppresses them (hypothalamic ascorbic acid). L-thyroxine evidently blocks the action of oestradiol in the adenohypophysis, the liver and the hypothalamus; the significance of this inhibition is discussed in relation to dopaminergic modulation of the adenohypophyseal reaction to oestradiol.     

The hyperglycemic effect of S-nitrosoglutathione in the dog.

The present study investigates the pharmacological activity of the nitric oxide (NO) donor S-nitrosoglutathione (GSNO) on the plasma glucose and insulin levels in healthy normoglycemic dogs. The plasma nitrate and nitrite concentrations were measured by a commercial autoanalyzer and taken as the biochemical markers of in vivo nitric oxide formation. Plasma glucose levels were measured by the glucose oxidase method, while the insulin levels were determined by radioimmunoassay. The possible effect of the coadministration of ascorbic acid (vitamin C) and GSNO on plasma glucose levels was also examined. In healthy normoglycemic dogs, administration of 35 and 50 mg/kg of GSNO caused a dose-dependent increase in postprandial plasma glucose levels. The plasma glucose levels were significantly elevated at the 1.5-, 2.0-, and 2.5-h time intervals of the oral glucose tolerance test at both concentrations of GSNO (P < 0.05). These values were significantly higher than those obtained using captopril (control). Furthermore, coadministration of 35 mg/kg of GSNO and 50 mg/kg ascorbic acid enhanced the postprandial hyperglycaemic effect observed for the administration of only 35 mg/kg of GSNO. There was a 35-100% increase in plasma nitrate concentration on administration of both doses of GSNO. Intravenous administration of GSNO (35 mg/kg) and captopril (20 mg/kg) significantly decreased the mean arterial blood pressure and increased the heart rate. The blood pressure-lowering effect of these drugs was more pronounced on systolic than on diastolic blood pressure (P < 0.05). These results suggests that in healthy normoglycaemic dogs: (a) nitric oxide released from GSNO increases postprandial plasma glucose levels and inhibits glucose-stimulated insulin secretion, (b) ascorbic acid enhances the postprandial hyperglycaemic effect of GSNO, probably by increasing the release of NO, and (c) GSNO decreases mean arterial blood pressure and increase heart rate in normotensive dogs.     

Mechanism of enhanced bioavailability and diuretic effect of azosemide by ascorbic acid in rats

To increase the extent of comparative oral bioavailability (F) value and the diuretic and natriuretic effects of orally administered azosemide, ascorbic acid was coadministered to rats. The rationales for this study are that ascorbic acid might inhibit intestinal first-pass effect of azosemide and might increase the unionized fraction of azosemide at the receptor sites. After oral administration of azosemide (20 mg/kg) with 100 mg of ascorbic acid, the F value (138% vs. 100%), 8-h urinary excretion of azosemide (5.18% vs. 1.32% of oral dose), 8-h urine output (41.3 vs. 23.0 ml), and 8-h urinary excretion of sodium (24.6 vs. 15.3 mmol/kg) were greater than controls (without ascorbic acid). The amount of spiked azosemide remaining after 30 min incubation of 50 mug of azosemide with the 9000 g supernatant fraction of rat small intestine was significantly greater by 100 microg of ascorbic acid (45.3 vs. 40.9 microg) than controls (without ascorbic acid). After oral administration of azosemide with NH4Cl, the urine pH decreased by 0.5 U, and 8-h urine output (25.8 vs. 11.0 ml) and 8-h urinary excretion of sodium (13.3 vs. 6.89 mmol/kg) were significantly greater than controls (without NH4Cl). The increase in F value and diuretic and natriuretic effects of azosemide with coadministration of ascorbic acid seemed to be due to reduced intestinal first-pass metabolism of azosemide, increased urinary excretion of azosemide, and increased unionized fraction of azosemide at the renal tubular receptor sites.     

Influence of ascorbic acid on the thermic effect of feeding in overweight and obese adult humans

The thermic effect of feeding (TEF: increase in energy expenditure following acute energy intake) is an important physiological determinant of total daily energy expenditure and thus energy balance. Approximately 40% of TEF is believed to be mediated by sympathoadrenal activation and consequent beta-adrenergic receptor stimulation of metabolism. In sedentary adults, acute administration of ascorbic acid, a potent antioxidant, augments the thermogenic response to beta-adrenergic stimulation. We hypothesized that acute ascorbic acid administration augments TEF in sedentary overweight and obese adults. Energy expenditure was determined (ventilated hood technique) before and 4 h after consumption of a liquid-mixed meal (caloric equivalent 40% of resting energy expenditure (REE)) in 11 sedentary, overweight/obese adults (5 men, 6 women; age: 24 +/- 2 years; BMI: 28.5 +/- 1.0 kg/m(2) (mean +/- s.e.)) on two separate, randomly ordered occasions: during continuous intravenous administration of saline (placebo control) and/or ascorbic acid (0.05 g/kg fat-free mass). Acute ascorbic acid administration prevented the increase in plasma concentration of oxidized low-density lipoprotein in the postprandial state (P = 0.04), but did not influence REE (1,668 +/- 107 kcal/day vs.1,684 +/- 84 kcal/day; P = 0.91) or the area under the TEF response curve (33.4 +/- 2.4 kcal vs. 30.5 +/- 3.6 kcal; P = 0.52) (control vs. ascorbic acid, respectively). Furthermore, acute ascorbic acid administration had no effect on respiratory exchange ratio, heart rate, or arterial blood pressure in the pre- and postabsorptive states (all P > 0.64). These data imply that the attenuated TEF commonly observed with sedentary lifestyle and obesity is not modulated by ascorbic acid-sensitive oxidative stress.     

The Hyperglycemic Effect of S-Nitrosoglutathione in the Dog

The present study investigates the pharmacological activity of the nitric oxide (NO) donor S-nitrosoglutathione (GSNO) on the plasma glucose and insulin levels in healthy normoglycemic dogs. The plasma nitrate and nitrite concentrations were measured by a commercial autoanalyzer and taken as the biochemical markers of in vivo nitric oxide formation. Plasma glucose levels were measured by the glucose oxidase method, while the insulin levels were determined by radioimmunoassay. The possible effect of the coadministration of ascorbic acid (vitamin C) and GSNO on plasma glucose levels was also examined. In healthy normoglycemic dogs, administration of 35 and 50 mg/kg of GSNO caused a dose-dependent increase in postprandial plasma glucose levels. The plasma glucose levels were significantly elevated at the 1.5-, 2.0-, and 2.5-h time intervals of the oral glucose tolerance test at both concentrations of GSNO (P < 0.05). These values were significantly higher than those obtained using captopril (control). Furthermore, coadministration of 35 mg/kg of GSNO and 50 mg/kg ascorbic acid enhanced the postprandial hyperglycaemic effect observed for the administration of only 35 mg/kg of GSNO. There was a 35–100% increase in plasma nitrate concentration on administration of both doses of GSNO. Intravenous administration of GSNO (35 mg/kg) and captopril (20 mg/kg) significantly decreased the mean arterial blood pressure and increased the heart rate. The blood pressure-lowering effect of these drugs was more pronounced on systolic than on diastolic blood pressure (P < 0.05). These results suggests that in healthy normoglycaemic dogs: (a) nitric oxide released from GSNO increases postprandial plasma glucose levels and inhibits glucose-stimulated insulin secretion, (b) ascorbic acid enhances the postprandial hyperglycaemic effect of GSNO, probably by increasing the release of NO, and (c) GSNO decreases mean arterial blood pressure and increase heart rate in normotensive dogs.     

Modulation of the effect of oestradiol on adenohypophyseal weight: ineffectiveness of nickel chloride, potentiation by cimetidine

Male rats received an i.m. injection of oestradiol benzonate twice a weak, as an aqueous microcrystal suspension in doses of 1 mg, and/or were given, in their food, nickel chloride in daily doses of 10 mg [first experiment] or 20 mg [second experiment] per rat, or cimetidine, an antagonist of H2 receptors, in daily doses of 20 mg [first experiment] or 40 mg [second experiment] per rat. Neither dose of nickel chloride affected the oestrogen-induced growth reaction of the adenohypophysis, the increase in polyphenol oxidase [ceruloplasmin] activity in the blood [the larger dose stimulated it slightly], the increase in hypothalamic polyphenol oxidase activity or the post-oestrogen drop in the hypothalamic ascorbic acid concentration. Both doses of cimetidine potentiated the growth reaction of the adenohypophysis to oestrogens, but did not affect the blood polyphenol oxidase, the hypothalamic polyphenol oxidase or the hypothalamic ascorbic acid reaction. If administered alone, the larger dose of cimetidine mildly reduced serum polyphenol oxidase [ceruloplasmin] activity.     

Pulmonary bioavailability of ascorbic acid in an ascorbate-synthesising species,the horse

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p < 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p < 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.     

Subchronic administration of ascorbic acid elicits antidepressant-like effect and modulates cell survival signaling pathways in mice

In this study, we examined the ability of subchronic ascorbic acid administration to produce an antidepressant-like effect in the mouse tail suspension test (TST). Moreover, we investigated the effect of this vitamin on hippocampal and cerebrocortical brain-derived neurotrophic factor (BDNF) immunocontent, phosphorylation of protein kinase B (AKT), extracellular signal-regulated kinase (ERK), p38^MAPK and c-Jun. N-terminal kinase (JNK). Fluoxetine (10 mg/kg, positive control, po) or ascorbic acid (0.1 and 1 mg/kg, po), administered once daily for 21 days, produced a significant antidepressant-like effect in the TST. The significant effects obtained in protein immunocontents were: administration of ascorbic acid at 1 mg/kg induced an increase in AKT phosphorylation in cerebral cortex of mice. Ascorbic acid treatment (1 mg/kg), similar to fluoxetine, decreased hippocampal p38^MAPK but did not alter ERK or JNK phosphorylation. These results extend the data about the antidepressant-like effect of ascorbic acid by exploring, for the first time, the intracellular pathways involved in its antidepressant properties after subchronic administration.     

Effects of dietary copper on human autonomic cardiovascular function

Heart rate and blood pressure responses during supine rest, orthostasis, and sustained handgrip exercise at 30% maximal voluntary contraction were determined in eight healthy women aged 18-36 years who consumed diets varying in copper and ascorbic acid content. Copper retention and plasma copper concentration were not affected by diet. Enzymatic, but not immunoreactive, ceruloplasmin was lower (p less than 0.05) after the low copper and high ascorbic acid diet periods. Diet had no effect on resting supine heart rates, orthostatic responses in heart rate and blood pressure, or standing resting blood pressure. Systolic and diastolic blood pressures were increased significantly (p less than 0.05) during the handgrip test at the end of the low copper and ascorbic acid supplementation periods. Also, the ratio of enzymatic to immunoreactive ceruloplasmin decreased significantly during these dietary treatments. The mean arterial blood pressure at the end of the handgrip test was negatively (p less than 0.0004) correlated with the ceruloplasmin ratios. These findings indicate a functional alteration in human blood pressure regulation during mild copper depletion.     

Changes in n-6 and n-3 polyunsaturated fatty acids during lipid-peroxidation of mitochondria obtained from rat liver and several brain regions: effect of alpha-tocopherol

The effect of intraperitoneal administration of alpha-tocopherol (100 mg/kg weight/24 h) on ascorbate (0-0.4 mM) induced lipid peroxidation of mitochondria isolated from rat liver, cerebral hemispheres, brain stem and cerebellum was examined. The ascorbate induced light emission in hepatic mitochondria was nearly completely inhibited by alpha-tocopherol (control-group: 114.32+/-14.4; vitamin E-group: 17.45+/-2.84, c.p.m.x10(-4)). In brain mitochondria, 0.2 mM ascorbate produced the maximal chemiluminescence and significant differences among both groups were not observed. No significant differences in the chemiluminescence values between control and vitamin E treated groups were observed when the three brain regions were compared. The light emission produced by mitochondrial preparations was much higher in cerebral hemispheres than in brain stem and cerebellum. In liver and brain mitochondria from control group, the level of arachidonic acid (C20:4n6) and docosahexaenoic acid (C22:6n3) was profoundly affected. Docosahexaenoic in liver mitochondria from vitamin E group decreased by 30% upon treatment with ascorbic acid when compared with mitochondria lacking ascorbic acid. As a consequence of vitamin E treatment, a significant increase of C22:6n3 was detected in rat liver mitochondria (control-group: 6.42 +/-0.12; vitamin E-group: 10.52 +/-0.46). Ratios of the alpha-tocopherol concentrations in mitochondria from rats receiving vitamin E to those of control rats were as follows: liver, 7.79; cerebral hemispheres, 0.81; brain stem, 0.95; cerebellum, 1.05. In liver mitochondria, vitamin E shows a protector effect on oxidative damage. In addition, vitamin E concentration can be increased in hepatic but not in brain mitochondria. Lipid peroxidation mainly affected, arachidonic (C20:4n6) and docosahexaenoic (C22:6n3) acids.     

Ascorbic acid supplementation and copper status in rats

The effect of a high concentration (1%, w/w) of ascorbic acid in a Cu-adequate (150 μmol/kg) purified diet was studied in rats. After 6 wk, ascorbic acid had significantly reduced Cu concentrations in muscle and bone. The estimated whole body content of Cu in rats fed ascorbic acid was reduced by 20%. Within 1 d after oral administration of⁶⁴Cu, the recovery of the dose in feces was increased in rats fed ascorbic acid, suggesting that the vitamin depresses intestinal absorption of Cu. After intraperitoneal (ip) administration of⁶⁴Cu, the rate of loss of the dose from the body was decreased in rats fed ascorbic acid. This study suggests that the ascorbic acid induces a decreased efficiency of intestinal Cu absorption, which in turn triggers mechanisms to preserve Cu in the body stores. This is supported by the observation that the feeding of a Cu-deficient diet (5 μmol/kg) had similar effects, although more pronounced.     

Effect of ascorbic acid concentration on the ESR signal intensity of dry tissue

A high concentration (r greater than 0.9; p less than 0.001) between the intensity of free radical ESR-signal (delta H max = 8-10 oe, g-factor 2.0057) in dry tissues of various organs of quinea pigs and concentration of free ascorbic acid in the same tissues was detected. Additional administration of ascorbic acid did not affect the correlation value of organs. The correlation coefficient was low in blood of control animals (r = 0.27; p greater than 0.05) and increased after administration of ascorbic acid (r = 0.95; p less than 0.001).     

GM1 ganglioside attenuates convulsions and thiobarbituric acid reactive substances production induced by the intrastriatal injection of methylmalonic acid

The effects of the administration of monosialoganglioside (GM1) on methylmalonic acid (MMA)-induced convulsions, production of thiobarbituric acid reactive substances (TBARS) and on the striatal content of ascorbic acid and total non-protein thiol (SH) groups were evaluated in adult male rats. Animals received two intraperitoneal injections of GM1 (50 mg/kg) or saline (0.85% NaCl) spaced 24h apart. Thirty minutes after the second GM1 or saline injection, L-MMA (6 micromol) or NaCl (9 micromol) was injected into the right striatum and the animals were observed for the appearance of convulsions for 15 min. The animals were sacrificed and their striatal content of ascorbic acid, SH groups and TBARS was measured. The effect of GM1 on MMA-induced TBARS production in striatal homogenates was also evaluated in vitro.MMA injection caused convulsions (Sal-MMA: 9.8+/-1.4 episodes, which lasted 271+/-48 s) and increased the striatal content of TBARS (Sal-MMA: 149.0+/-11.5 nmol MDA/g tissue), but did not alter total striatal SH or ascorbic acid contents. GM1 pretreatment decreased MMA-induced convulsions (GM1-MMA: 6.3+/-2.0 episodes, which lasted 115.1+/-42.2s) and TBARS increase (GM1-MMA: 102.4+/-19.5 nmol MDA/g tissue). GM1 pretreatment increased ascorbic acid content of the striata (saline-pretreated: 1514+/-75.9; GM1-pretreated: 1878.6+/-102.8 microg ascorbic acid/mg tissue). MMA increased TBARS production in vitro, and GM1 had no effect on such MMA-induced effect.This study provides evidence that GM1 increases striatal ascorbic acid content and decreases MMA-induced neurotoxicity assessed by behavioral and neurochemical parameters.     

Lack of effect of experimental ascorbic acid deficiency on bile acid metabolism, sterol balance, and biliary lipid composition in man

Extensive studies in animal models indicate that subclinical ascorbic acid deficiency impairs the conversion of cholesterol to bile acid, elevates plasma cholesterol levels, and predisposes to development of cholesterol cholelithiasis. The present study was designed to see if this is also true in man. Five normal volunteers were hospitalized in a metabolic ward and placed on a controlled diet containing 3-4 mg of ascorbic acid each day. Ascorbic acid supplementation was given as follows: control period I (days 1-33), 75 mg/day; deficient period (days 34-96), 0 mg/day; and repletion period (days 97-101), 1000 mg/day. In addition, three of the subjects were studied during a second control period (days 102-139) during which they were given 75 mg/day of ascorbic acid. Ascorbate levels at the end of both control periods were 0.87-1.34 mg/dl in plasma and 19.4-29.5 micrograms/10(8) cells in leukocytes. At the end of the deficient period these levels were 0.09-0.15 mg/dl in plasma and 6.2-10.0 micrograms/10(8) cells in leukocytes, levels approaching those seen in scurvy. There was no effect of ascorbic acid deficiency on plasma cholesterol and triglycerides; plasma cholesterol in high, very low, and low density lipoprotein fractions; biliary lipid composition and saturation index of gallbladder bile; synthesis, fractional turnover, or pool size of either cholic or chenodeoxycholic acids; output of fecal acid or neutral sterols; and fecal sterol balance. Total bile acid pool size calculated by the one-sample technique was reduced 11% in the deficient period compared to control period I (P less than 0.005), and increased to 98.7% of the baseline levels in control period II. However, total bile acid pool calculated by the Lindstedt method did not change during deficiency. These data demonstrate that short-term subclinical ascorbic acid deficiency near the scorbutic range has no significant effect on bile acid and cholesterol metabolism in man.     

Changes in the blood parameters of an air-breathing fish during different respiratory conditions.

Some of the blood parameters recorded in an air-breathing eel, Amphipnous cuchia under normal respiratory condition during non-breeding period (September-April) are haemoglobin (Hb) concentration 19.26%, haematocrit value 56.16%, RBC number 1.71 million/mm3, RBC size 18.86 X 9.70 mum, mean corpuscular haemoglobin (MCH) 113.4 ng, mean corpuscular haemoglobin concentration (MCHC) 34.2%, blood sugar 77 mg% and ascorbic acid 0.435 mg%. The higher concentration of haemoglobin (19.26%) appears to be related to its obligatory air breathing habit and habitat in a water of low oxygen content. Though a definite trend of increase in the haemoglobin and haematocrit concentration with an increase in the body weight of the fish was lacking, variations were clearly marked related to intrinsic activity of the fish connected with different respiratory conditions. Asphyxiation in a submerged but continuous flow of water (liter/h) for 5 1/2 h resulted in an increase in the above-mentioned parameters to an appreciable extent. These increases were 0.23 million/mm3 in the number of erythrocytes, 6.16% in haemoglobin concentration, 10% in haematocrit value, 20% in blood sugar and 35% in ascorbic acid content. The mean corpuscular haemoglobin showed a decline of 6.2%. Exclusive aerial breathing for 5 1/2 h also caused 7.4% increase in haemoglobin concentration, 9.4% in haematocrit value, 0.14 million/mm3 in RBC number, 20% in blood sugar level, 9% in ascorbic acid content but almost no change in mean corpuscular haemoglobin. The average surface area for diffusion of gases appeared to have reduced by 6.8 mum2 per RBC.     

A newly established strain of spontaneously hypertensive rat with a defect of ascorbic acid biosynthesis.

To investigate the effects of ascorbic acid deficiency on the pathogenesis of hypertension and/or its complications, we established a rat strain with both genetic hypertension and a defect of ascorbic acid biosynthesis. The od gene (L-gulono-gamma-lactone oxidase gene) of the ODS (Osteogenic Disorder Shionogi) rat, which is a rat mutant unable to synthesize ascorbic acid, was introduced into spontaneously hypertensive rats (SHR), and a novel congenic strain, SHR-od, was established. SHR-od showed scurvy when fed an ascorbic acid-free diet. Systolic blood pressure of male SHR-od began to increase at 9 weeks of age and reached 190-200 mmHg at 20 weeks of age. In 25-week-old SHR-od, ascorbic acid deficiency when fed an ascorbic acid-free diet for 6 weeks caused a remarkable reduction of blood pressure to lower than 110 mmHg. The wall to lumen ratio of the testicular artery in ascorbic acid-deficient SHR-od was lower than that of the control rats. When rats were fed a diet supplemented with ascorbic acid (300 mg/kg), ascorbic acid concentration in SHR-od was lower in the serum and liver than that in ODS rats. These results indicate that ascorbic acid could be closely related to the development of hypertension in SHR-od. We believe that SHR-od will be a useful model for experimental studies on hypertension and its complications, since all of them suffer from hypertension spontaneously and the level of ascorbic acid deficiency in these rats could be controlled at will both in concentration and duration.     

Protective role of curcumin against isoproterenol induced myocardial infarction in rats

The effect of curcumin on the biochemical changes induced by isoproterenol (ISO) administration in rats was examined. ISO (300 mg Kg^–1 administered subcutaneously twice at an interval of 24 h) caused a decrease in body weight and an increase in heart weight, water content as well as in the levels of serum marker enzymes viz creatine kinase (CK), lactate dehydrogenase (LDH) and LDH₁ isozyme. It also produced electrocardiographic changes such as increased heart rate, reduced R amplitude and ST elevation. Curcumin at a concentration of 200 mg.Kg^–1 when administered orally, showed a decrease in serum enzyme levels and the electrocardiographic changes got restored towards normalcy. Myocardial infarction was accompanied by the disintegration of membrane polyunsaturated fatty acids expressed by increase of thiobarbituric acid reactive substance (TBARS), a measure of lipid peroxides and by the impairment of natural scavenging, characterized by the decrease in the levels of superoxide dismutase, catalase, glutathione peroxidase, ceruloplasmin, alpha tocopherol, reduced glutathione (GSH) and ascorbic acid. The oral pretreatment with curcumin two days before and during ISO administration decreased the effect of lipid peroxidation. It was shown to have a membrane stabilizing action by inhibiting the release of -glucuronidase from nuclei, mitochondria, lysosome and microsome. Curcumin pre- and co-treatment decreased the severity of pathological changes and thus, could have a protective effect against the damage caused by myocardial infarction (MI).     

Effect of thiamine, riboflavin and ascorbic acid on tetracycline, erythromycin and levomycetin activity]

The effect of antibiotics was estimated by inhibition of the protein increase in the broth culture of Staph, aureus during incubation at a temperature of 37 degrees for 18 hours. In some experiments preincubation of the antibiotic solutions with the vitamins for 2 hours at light and in dark was used. The antibiotic concentrations in gamma per 1 ml were equal to those of the vitamins. In the experiments with tetracycline and 2-hour preincubation at light the antibiotic in a concentration of 0.1gamma ml inhibited for certain the protein increase by 58.9%, in combination with thiamin it inhibited the protein by 60 per cent and in combination with ascorbic acid by 59%. Riboflavin lowered the activity of tetracycline to a value not differing for certain from the control one. In the experiments with preincubation in dark tetracycline inhibited the protein increase by 55.2%, in combination with thiamin it inhibited the protein increase by 50.5%, in combination with riboflavin by 53% and in combination with ascorbic acid by 57.2%. Erythromycin in a concentration of 0.03gamma/ml when preincubated at light inhibited the protein increase by 48.8% and in combinations with thiamin, riboflavin or ascorbic acid by 23, 27, 47.2% respectively. When preincubated in the darkness erythromycin alone inhibited the protein increase by 47.8% and in combinations with thiamin, riboflavin or ascorbic acid by 32.5, 51.1 or 49.8% respectively. The above vitamins has no effect on levomycetin activity.     

Ascorbic acid does not affect the age-associated reduction in maximal cardiac output and oxygen consumption in healthy adults.

Maximal aerobic capacity (Vo(2max)) decreases progressively with age, primarily because of a reduction in maximal cardiac output (Q(max)). This age-associated decline in Vo(2max) may be partially mediated by the development of oxidative stress that can suppress beta-adrenergic-receptor responsiveness and, consequently, reduce Q(max). To test this hypothesis, Vo(2max) (indirect calorimetry) and Q(max) (open-circuit acetylene breathing) were determined in 12 young (23 +/- 1 yr, mean +/- SE) and 10 older (61 +/- 1 yr) adults following systemic infusion of either saline (control) and/or the powerful antioxidant ascorbic acid (acute: bolus 0.06; drip 0.02 g/kg fat-free mass) and following chronic 30-day oral administration of ascorbic acid (500 mg/day). Plasma ascorbic acid concentration was not different between young and older adults and was increased similarly, independent of age [change (Delta) acute = 1,055 +/- 117%; Delta chronic = 62 +/- 19%]. Oxidized low-density lipoprotein concentration was greater (P < 0.001) in older (57 +/- 5 U/l) compared with young (34 +/- 3 U/l) adults and was reduced in both groups (P < 0.02) following acute (Delta = -6 +/- 2%) but not chronic (P = 0.18) ascorbic acid administration. Control (baseline) Vo(2max) and Q(max) were positively related (r = 0.76, P < 0.001) and were lower (P < 0.05) in older (34 +/- 2 ml.kg(-1).min(-1); 16.1 +/- 1.1 l/min) compared with young (43 +/- 3 ml.kg(-1).min(-1); 20.2 +/- 0.9 l/min) adults. Following ascorbic acid administration, neither Vo(2max) (young acute = 41 +/- 2; young chronic = 42 +/- 2; older acute = 34 +/- 2; older chronic = 34 +/- 2 ml.kg(-1).min(-1)) nor Q(max) (young acute = 20.1 +/- 0.9; young chronic = 19.1 +/- 0.8; older acute = 16.2 +/- 1.1; older chronic = 16.6 +/- 1.4 l/min) was changed. These data suggest that ascorbic acid administration does not affect the age-associated reduction in Q(max) and Vo(2max).     

Evaluation of plasma antioxidant activity in rats given excess EGCg with reference to endogenous antioxidants concentrations and assay methods

The contribution of (?)-epigallocatechin gallate (EGCg) intake to in vivo antioxidant activity is unclear, even with respect to plasma. In this study, we examined how administration of EGCg contributes to plasma antioxidant activity, relative to its concentration, endogenous antioxidants, and assay methods, namely oxygen radical absorbance capacity (ORAC) and ferric reducing/antioxidant power (FRAP). Administration of EGCg (500?mg/kg) to rats increased plasma EGCg (4μmol/L as free form) and ascorbic acid (1.7-fold), as well as ORAC (1.2-fold) and FRAP (3-fold) values. The increase in plasma ascorbic acid following EGCg administration was accompanied by its relocation from the adrenal glands and lymphocytes into plasma, and was related to the increase in FRAP. Plasma deproteinization and assays in plasma model solutions revealed that protein levels significantly contributed to ORAC values, where <3?μmol/L EGCg in the presence of protein exhibited minimal antioxidant activity, as measured by both FRAP and ORAC. As the concentration of plasma ascorbic acid was not influenced by deproteinization, differences in FRAP values with and without deproteinization were estimated to determine the contribution of enhanced ascorbic acid attributable to EGCg administration. These results will help to understand the points that should be considered when evaluating EGCg antioxidant activity in plasma.