Effects of fasting, body weight, methylcellulose, and carboxymethylcellulose on hepatic glutathione levels in mice and hamsters

1: Final Report on the Safety Assessment of Hydroxyethylcellulose, Hydroxypropylcellulose, Methylcellulose, Hydroxypropyl Methylcellulose, and Cellulose Gum

Hydroxyethylcellulose, Hydroxypropylcellulose, Methylcellulose, Hydroxypropyl Methylcellulose, and Cellulose Gum are modified cellulose polymers that are used in cosmetic products at concentrations up to 10%. The cellulose derivatives pass essentially unchanged through the gastrointestinal tract following oral administration. They are practically nontoxic when administered by inhalation or by oral, intraperitoneal, subcutaneous, or dermal routes. Subchronic and chronic oral studies indicate that the cellulose derivatives are nontoxic when administered to laboratory animals. No significant teratogenic or reproductive effects have been demonstrated. Ocular and dermal irritation studies show that the cellulose derivatives are, at most, minimally irritating to rabbit eyes and nonirritating to slightly irritating to rabbit skin when tested at concentrations up to 100%. No mutagenic activity of theseingredients was demonstrated. The cellulose derivatives at concentrations up to 100% were nonirritating to mildly irritating, nonsensitizing, and nonphotosensitizing when evaluated in clinical studies. It is concluded that theingredients reviewed are safe as cosmeticingredients in the present practices of use and concentration.

Fasting of mice: a review

Fasting of mice is a common procedure performed in association with many different types of experiments mainly in order to reduce variability in investigatory parameters or to facilitate surgical procedures. However, the effects of fasting not directly related to the investigatory parameters are often ignored. The aim of this review is to present and summarize knowledge about the effects of fasting of mice to facilitate optimization of the fasting procedure for any given study and thereby maximize the scientific outcome and minimize the discomfort for the mice and hence ensure high animal welfare. The results are presented from a number of experimental studies, providing evidence for fasting-induced changes in hormone balance, body weight, metabolism, hepatic enzymes, cardiovascular parameters, body temperature and toxicological responses. A description of relevant normal behaviour and standard physiological parameters is given, concluding that mice are primarily nocturnal and consume two-thirds of their total food intake during the night. It is argued that overnight fasting of mice is not comparable with overnight fasting of humans because the mouse has a nocturnal circadian rhythm and a higher metabolic rate. It is suggested that because many physiological parameters are regulated by circadian rhythms, fasting initiated at different points in the circadian rhythm has different impacts and produces different results.

Optimization and application of glutamate cysteine ligase measurement in wildlife species

Glutamate cysteine ligase (GCL), synthesizing gamma-glutamylcysteine from glutamate and cysteine, is the rate-limiting enzyme in glutathione (GSH) biosynthesis. GCL activity measurement was optimized in tissues from deer mice, Sprague Dawley rats, and mallard ducks. Varying glutamic acid concentrations from 5 to 80 mM did not affect GCL activities markedly, whereas cysteine concentrations from 2.5 to 40 mM influenced GCL activities substantially. Optimal cysteine concentrations for deer mouse, Sprague Dawley rat, and mallard duck (respectively) were 30, 30, and 20 mM in liver, 10, 10, and 20 mM in kidney, 20, 20, and 30 mM in brain, and 30 mM in heart for all three species. Responses of mallard duck GCL activity to acid metalliferous water were evaluated. After subacute exposure, low doses increased GCL activity and GSH content in liver by 48.3% and 54.4%, respectively. High doses reduced GCL activities significantly in liver and kidney to 31.2% and 43.0% of the control, respectively.

Effects of acclimation and incubation temperature on the glutathione antioxidant system in killifish and RTH-149 cells

Glutathione (GSH) is an important antioxidant that is involved in a multitude of cellular processes. However, in fish, GSH levels, turnover, and activity of associated enzymes are low when compared to those of mammals. To determine whether temperature influences the GSH antioxidant system in fish, and can explain the differences in GSH between fish and mammals, we examined the effects of acclimation temperature on total GSH (tGSH) levels and apparent half-life (as an estimate of turnover) in a rainbow trout hepatoma cell line (RTH-149), and GSH levels, and glutathione peroxidase (GPx) and reductase (GR) activity in the eurythermal killifish. Increasing incubation temperature decreased half-life and transiently increased levels of tGSH in RTH-149 cells. In killifish, increased acclimation temperature increased tGSH levels in the liver, brain and muscle, and increased hepatic GPx and GR activities. When the relationships between temperature and GSH half-life, levels and enzyme activity were extrapolated to 37 degrees C, temperature could only partially accounted for differences in the GSH antioxidant system in fish compared to mammals. The differences in the GSH antioxidant system between fish and mammals may not be solely due to temperature effects, but also to the increased metabolic cost of endothermy in mammals.

Glutathione content of the small intestine: regulation and function

In ad lib.-fed rats the epithelium of the small intestine, like the liver, contains large quantities of glutathione, 17.0 and 32.4 nmol/mg protein respectively. Following 24 h food restriction the glutathione content in both tissues fell 53 and 69% respectively. Unlike the liver, however, the glutathione content of the intestinal mucosa is not regulated to a diurnal rhythm, suggesting that the liver may provide glutathione or glutathione precursors to maintain intestinal glutathione levels. Intestinal epithelial cell preparations obtained from 24 h food-deprived rats had depleted glutathione stores (50%) and as a consequence were more susceptible to the oxidizing effects of cumene hydroperoxide. These results suggest that if glutathione plays a major role in the defence of the intestinal mucosa from ingested toxins then depletion of this defence during periods of food restriction could significantly increase the susceptibility of the individual to toxins present in the diet.

Differing response of the glutathione system to fasting in neonatal and adult guinea pigs

Adult, term neonatal and 3 day preterm neonatal guinea pigs were fasted for 48 hr, and the glutathione concentrations of the liver and lung assessed. In adult animals, glutathione concentration decreased by 43% in the liver and 29% in the lung with respect to fed controls. The decrease in liver glutathione was associated with a 75% reduction in the hepatic activity of tau-glutamyltranspeptidase (tau GGT). Conversely, both liver and lung glutathione levels in preterm pups remained unchanged following 48 hr food restriction. Likewise, hepatic tau GGT, glutathione reductase (GRed) and glutathione peroxidase (GPx) activities were unchanged by fasting in preterm pups. Fasting increased pulmonary GPx activity by 27% in these pups. In fasted, term animals, substantial increases in both lung (65%) and liver (80%) glutathione concentrations were observed, with concomitant increases in GPx and GRed activities. Hepatic tau GGT activity was significantly reduced (57%) in term pups. These results may suggest that the neonatal guinea pig can maintain tissue glutathione status during periods of nutrient stress, through an increased capacity for recycling oxidized glutathione and a decrease in turnover of the tripeptide. Guinea pig neonates are therefore able to resist starvation-induced decreases in tissue glutathione levels seen in adult rodents. If this is a general neonatal response it may have important clinical implications in the treatment of preterm babies.

Effect of in vivo chromate, acetone and combined treatment on rat liver in vitro microsomal chromium(VI) reductive activity and on cytochrome P450 expression

Cytochrome P450 (P450IIE1) in rat has previously been shown to exhibit high chromate [Cr(VI)] reductase activity (Mikalsen et al. 1991). The present study reports on the effect of chromate treatment in vivo in rats and on the modulating effect of acetone + fasting on chromium(VI) toxicity. No effect of intraperitoneal injection with 5 mg chromate/kg was observed, whereas 15 mg chromate/kg decreased the liver microsomal Cr(VI) reductase activity by about 30% in in vitro microsomal incubations. In addition, the P450 and cytochrome b5 contents were decreased by about 30% and 25% respectively. Acetone + fasting caused increases of total microsomal P450 and cytochrome b5 contents, associated with similar increases in apoproteins P450IIE1 and P450IIB1 + 2, and their corresponding mRNA, and apoprotein NADPH-P450 reductase, as well as NADPH-P450 reductase and microsomal Cr(VI) reductive activities. Related to acetone + fasting alone, when given in combination with chromate (15 mg/kg) the Cr(VI) reductive activity was decreased by about 30%, associated with decreases in the P450 and cytochrome b5 contents, 65% and 35% respectively. This further reduced the apoprotein levels of P450IIB1 + 2, P450IIE1, and NADPH-P450 reductase to 90%, 60%, and 40%, respectively, and the mRNA levels of P450IIB2 and P450IIE1. No effect was observed on NADPH-P450 reductase activity. This dose also caused some macroscopic alterations in the liver. In contrast, the P450IIE1 apoprotein level in the lung was apparently stabilized or even increased by chromate in rats treated with acetone + fasting.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of methylcellulose on hepatic glutathione levels and plasma ALAT following single oral administration to male Bom:NMRI mice

1. A single p.o. dose of 1% w/v methylcellulose 0.013 ml/kg was given to male Bom:NMRI mice using untreated animals as controls. 2. A circadian fluctuation was seen in the hepatic glutathione levels (GSH) of both the methylcellulose and untreated animal group. 3. The methylcellulose administration did not affect the hepatic GSH or plasma ALAT level compared to untreated animals. 4. Histological examination did not reveal any abnormalities of the stomach wall, liver or kidney during the 12 hr trial period. 5. Male Bom:NMRI mice treated with 1% w/v methylcellulose can be considered representative of untreated controls in short-term experiments studying liver GSH and plasma ALAT levels.

Diurnal fluctuation and pharmacological alteration of mouse organ glutathione content

Mouse liver glutathione content showed a diurnal variation with a maximum GSH + 2 GSSG content at 6 to 10 a.m. of 62 +/- 8 nmole per mg protein and a minimum of 42 +/- 7 at 6 p.m. Starvation for more than 24 hr decreased the hepatic glutathione content to 22 +/- 3 nmole/mg protein and abolished the diurnal rhythm. Artificial reversal of the feeding habit of the animals reversed the diurnal rhythm. Kidney, spleen and lung glutathione contents showed no such rhythm. The organ glutathione content decreased by 50% or more upon starvation. The increase of the liver glutathione content by injection of either free or liposomally entrapped GSH to starved animals was not dependent on the time of administration. The physiological maximum level could not be exceeded by this treatment. It was not possible to influence the glutathione content of kidney, lung or intestine by glutathione injections in either form. Intravenous injections of equimolar doses of 2,3-dimercaptopropanol, 2-mercaptoethanesulfonic acid, N-2-mercaptopropionylglycine, D-penicillamine, or cysteamine did not lead to any significant change in liver, kidney, spleen or lung glutathione contents 2 hr after administration. Intravenously given N-acetylcysteine, methionine, GSH or GSSG restored liver glutathione levels of starved animals to the contents observed in the fed state. The diurnal hepatic variation of GSH caused by the food intake habit of the animals may limit the capacity of the intracellular detoxication system.

Detoxication of industrial pollutants by the glutathione glutathione-S-transferase system in the liver of Anabas testudineus (Bloch)

The interrelationship of reduced glutathione (GSH) and glutathione-S-transferase in the liver of a freshwater climbing perch Anabas testudineus (Bloch) exposed to common industrial pollutants has been studied. In both short- and long-term treatments there was a concomitant decrease in reduced glutathione profile and an increase in glutathione-S-transferase activity. It may be surmised that the majority of xenobiotics of industrial origin are detoxicated by the glutathione glutathione-S-transferase pathways enabling the fish to survive exposure to the additive and/or synergistic toxicity of mixtures of poisons.

Peroxisomal beta-oxidation from endogenous substrates. Demonstration through H2O2 production in the unanaesthetized mouse

A system was developed in which it is possible to detect in vivo changes in hepatic H2O2 production, using a combination of the catalase inhibitor, 3-amino-1,2,4-triazole and methanol. In mice, starvation significantly increases hepatic H2O2 production and plasma non-esterified fatty acid concentrations. Short-term refeeding after a 24 h starvation period brings H2O2 production and plasma non-esterified fatty acid concentration back to normal in 3h. Administration of insulin 24 h after the onset of starvation normalizes H2O2 production in less than 2h and decreases non-esterified fatty acid concentration below normal values. The suppression by insulin of H2O2 production, as well as its coherence with plasma non-esterified fatty acid concentration, indicate that increased H2O2 production in starved mice reflects peroxisomal beta-oxidation.

Enhancement of paracetamol induced hepatotoxicity by prior treatment with carboxymethylcellulose

This study was undertaken to determine if interactions of toxicological significance might occur during treatment of mice with paracetamol (P) and carboxymethylcellulose (CMC). P (300 mg/kg) administration induced only slight hepatic morphologic changes and lowered hepatic reduced glutathione (GSH) to 40% of the level in controls, when measured 1 hour after treatment. Intraperitoneal pretreatment with CMC (1% in NaC1, 20 ml/kg), significantly decreased GSH concentration (to 19% of controls) and severely enhanced hepatic injury. Such an interaction is of considerable significance since both CMC and P are widely used substances in experimental pharmacology and clinical practice.

Enhancement of adriamycin toxicity by carboxymethylcellulose in mice

Carboxymethylcellulose (CMC) (1% in 0.9% NaCl, 0.2 ml/10 g ip) a common suspending agent, enhanced adriamycin (ADR) (15 mg/kg ip) toxicity when administered to mice 5 hr before the antibiotic. Compared with ADR alone, this combination treatment produced, after 7 days, an increase in lethality from 15 to 80%. The pathologic analysis of hearts, livers, kidneys, and small bowels was performed, revealing an increase in the incidence and severity of hepatic damage in mice receiving ADR + CMC. Furthermore, reduced glutathione (GSH) was measured in livers of all mice; the animals treated with CMC and ADR + CMC showed a significant (p less than 0.01) reduction of hepatic GSH in comparison with controls and ADR-alone-treated animals. These data further confirm a crucial protective role for GSH in ADR toxicity and prove that CMC exerts an important biochemical effect on hepatic GSH.

Ammonia-induced change in the hepatic glutathione level of an air-breathing freshwater teleost Channa punctatus (Bloch)

Exposure to ammonia (NH4OH) for 48 h resulted in greater than 50% depletion of the hepatic glutathione pool in Channa punctatus (Bloch). Removal of fish to ammonia free ambience induced a rapid and excessive resynthesis of glutathione within 24 h. This level, however, decreased within 5 days of return to ammonia-free fresh water. It is concluded that ammonia stress in a freshwater air-breathing teleost is counteracted by the glutathione system of detoxication of xenobiotics and resynthesis of glutathione is induced by short-term exposure to ammonia followed by transfer to ammonia-free water.

Effects of species, MFO inducers and conjugation agents on the in vitro covalent binding of 14C-3-methylindole metabolite in liver and lung tissues

The degree of tissue covalent binding of 14C-3-methylindole metabolite in goat and rat pretreated with phenobarbital or 3-methylcholanthrene was compared. The effect of conjugating agents, i.e. glutathione (GSH), cysteine and sulfate, in reducing the degree of tissue covalent binding was measured. The degree of tissue covalent binding was significantly higher in the lung than the liver of goats. In rats, covalent binding was higher in the liver than the lung. Glutathione and cysteine were effective in decreasing the degree of in vitro covalent binding in both liver and lung tissues of goat and rat.

Drug-induced lipid peroxidation in mice--III. Glutathione content of liver, kidney and spleen after intravenous administration of free and liposomally entrapped glutathione

The half-life of extracellular glutathione was found to be 1.9 min in fed mice with a hepatic glutathione content of 44 +/- 10 nmol glutathione per mg protein. It was 4.9 min in animals that had been fed for 48 hr a liquid sucrose diet resulting in a decreased hepatic glutathione of 25 +/- 7 nmol/mg. A single intravenous injection of 16.2 mumol liposomally entrapped glutathione led to an increase in hepatic glutathione to 45 nmol/mg in the sucrose-fed mice after 2 hr and had no effect in the fed group. The spleen glutathione content reached a maximum at 30 min after injection in both groups. The maximum uptake into liver was 21% of the applied dose, into the spleen 7% and into the kidneys 2.4%. Injection of glutathione in solution led to a similar increase of hepatic glutathione as observed with GSH-containing liposomes, while liposomes filled with the constituent amino acids had only a marginal effect. The spleen took up only liposomal GSH. In contrast, the kidney glutathione content increased within 10 min up to 150% upon injection of free glutathione. The findings are consistent with a rapid hydrolysis of extracellular free glutathione followed by an interorgan turnover utilizing the constituent amino acids for resynthesis in the liver. Pretreatment of the animals with the glutathione synthesis inhibitor buthionine sulfoximine essentially abolished the hepatic glutathione increase upon treatment with GSH-liposomes or with the free compound. The finding that only liposomally entrapped glutathione protects mice against liver necrosis induced by highly dosed paracetamol is discussed with respect to differential uptake and distribution of GSH-liposomes in the liver.