Postnatal exposure to Bisphenol S induces liver injury in mice: Possible implication of PPARγ receptor.

There is considerable evidence that Bisphenol S (BPS) induces various toxicological effects and is an industrial health issue. However, little data are available on the in vivo effects of BPS on the liver, a major target of drug toxicity. In this study, we evaluated the potential harmfulness of low levels of BPS in the liver of male mice. Also, we investigated the interaction between BPS and peroxisome proliferator-activated receptor-gamma (PPARγ) by computational docking approach. PPARγ is a member of the superfamily of nuclear hormone receptors. It acts as a transcription factor and regulates the genes involved in lipid and glucose metabolism and in inflammation and necrosis. Mice were exposed to BPS, in drinking water at 25, 50, and 100 µg/kg for 10 weeks. The protocol was started after weaning. At the time of sacrifice, blood samples were collected for a biochemical analysis, followed by liver tissue collection for histopathological study. Results showed that BPS-induced hypertriglyceridemia, increased liver injury markers, and initiated histopathological changes, including inflammatory cell infiltration, hepatocellular necrosis, and steatosis. BPS did not affect glycated hemoglobin (HbA1C). Interestingly, data showed that BPS could interact with the PPARγ ligand-binding pocket by hydrogen bonds with Asn 219, Cys 276, Ser 280, and Thr 283. We suggest that PPARγ is among the targets of BPS and could play a key role in the cascade reaction of BPS-induced liver disruption. These findings support the hypothesis that the post-weaning period is sensitive to low-dose BPS exposure that can lead to dyslipidemia signature later in life.

Cytogenetic and developmental toxicity of bisphenol A and bisphenol S in Arbacia lixula sea urchin embryos.

Bisphenol S (BP-S) is one of the most important substitutes of bisphenol A (BP-A), and its environmental occurrence is predicted to intensify in the future. Both BP-A and BP-S were tested for adverse effects on early life stages of Arbacia lixula sea urchins at 0.1 up to 100 µM test concentrations, by evaluating cytogenetic and developmental toxicity endpoints. Embryonic malformations and/or mortality were scored to determine embryotoxicity (72 h post-fertilization). It has been reported in academic dataset that bisphenols concentration reached µg/L in aquatic environment of heavily polluted areas. We have chosen concentrations ranging from 0.1-100 µM in order to highlight, in particular, BP-S effects. Attention should be paid to this range of concentrations in the context of the evaluation of the toxicity and the ecological risk of BP-S as emerging pollutant. Cytogenetic toxicity was measured, using mitotic activity and chromosome aberrations score in embryos (6 h post-fertilization). Both BP-A and BP-S exposures induced embryotoxic effects from 2.5 to 100 µM test concentrations as compared to controls. Malformed embryo percentages following BP-A exposure were significantly higher than in BP-S-exposed embryos from 0.25 to 100 µM (with a ~5-fold difference). BP-A, not BP-S exhibited cytogenetic toxicity at 25 and 100 µM. Our results indicate an embryotoxic potential of bisphenols during critical periods of development with a potent rank order to BP-A vs. BP-S. Thus, we show that BP-A alternative induce similar toxic effects to BP-A with lower severity.

Bisphenol S favors hepatic steatosis development via an upregulation of liver MCT1 expression and an impairment of the mitochondrial respiratory system.

Bisphenol S (BPS) is a common substitute of bisphenol A (BPA). Recent data suggest that BPS acts as an obesogenic endocrine disruptor with emerging implications in the physiopathology of metabolic syndrome. However, the effects of BPS on monocarboxylate transporters (acting as carriers for lactate, pyruvate, and ketone bodies) and the mitochondrial respiratory system in the liver remain limited. For this purpose, male Swiss mice were treated with BPS at 100 µg/kg/day for 10 weeks, in drinking water. An increase in body weight and food intake was observed with no increase in locomotor activity. Moreover, data show that BPS increases hepatic MCT1 (a key energetic fuel transporter) mRNA expression accompanied by hepatic steatosis initiation and lipid accumulation, while disrupting mitochondrial function and oxidative stress parameters. Furthermore, BPS produced a significant increase in lactate dehydrogenase and creatine kinase activities. We can suggest that BPS contributes to hepatic steatosis in mice by upregulating monocarboxylate transporters and affecting the bioenergetic status characterized by an impaired mitochondrial respiratory system. Thus, our data highlight a new mechanism putatively implicated in hepatic steatosis development during BPS-induced obesity involving lactate metabolism.

Low-dose bisphenol S exposure induces hypospermatogenesis and mitochondrial dysfunction in rats: A possible implication of StAR protein.

A wide variety of environmental chemicals/xenobiotics including bisphenol A (BPA) has been shown to cause male reproductive dysfunctions and infertility. Recently, bisphenol S (BPS) replaces BPA, in several products, including foodstuffs, under the BPA-free label. However, several studies have raised inquietude about the potential adverse effects of BPS. The present study was conducted to evaluate sperm parameters, biochemical parameters, mitochondrial function, and histopathological patterns after post-lactation BPS exposure at a low dose. Male rats (21 days old) were exposed to water containing BPS at 50 µg/L in drinking water for 10 weeks. Results showed no significant alteration in the gonadosomatic index (GSI) and relative reproductive organs weight. However, a significant reduction in epididymal sperm parameters (number, viability, and mobility) with morphological abnormalities were observed in the BPS group compared to control. An increase of malondialdehyde (MDA) level accompanied by antioxidant defense alteration particularly, in glutathione peroxidase activity, as well as a defective mitochondrial function were observed in testicular tissues of BPS treated rats. More importantly, in histopathological diagnosis, BPS treatment induces hypospermatogenesis and alteration in Sertoli cells. In silico docking studies illustrated BPS binds with steroidogenic acute regulatory (StAR) protein thereby affecting the transport of cholesterol into mitochondria resulting in decreased steroidogenesis. These results reflect a reprotoxic effect of BPS vould potentially lead to fertility reduction, in sexually maturity age. We highlighted that post-lactation exposure to BPS, equivalent in humans to the period covering childhood and adolescent stages, disrupt male reproduction function.

Effects of bisphenol S, a major substitute of bisphenol A, on neurobehavioral responses and cerebral monocarboxylate transporters expression in mice.

Bisphenol A has been restricted in a large variety of products. Bisphenol S (BPS) is its major substitute. Yet, the impacts of BPS on the central nervous system are unknown, especially in vulnerable populations like children. The aim of this study was to investigate the effects of BPS on behavioral performances and the expression of cerebral monocarboxylate transporters (MCTs). Male Swiss mice were exposed to BPS at 100 µg/kg in drinking water for 10 weeks. The protocol started after the lactation period, which is a sensitive period of early social-emotional development. Elevated T-maze and open field tests were used to measure respectively, anxiety-related and activity-related behaviors. Molecular expressions of MCTs isoforms (MCT1, MCT2, MCT4) were determined in the frontal cortex. Data showed that BPS does not affect mRNA expression of MCTs. However, BPS decreases the number of entries into the open arms and the time spent on them for BPS-treated mice. These data reveal an anxiogenic effect of BPS. For locomotor activity and exploratory behavior levels, differences did not reach a statistically significant level in the BPS-exposed group. The effect of BPS on behavioral performances unravels a putative risk for psychopathology development in early childhood and calls for more attention.

Bisphenol S exposure affects gene expression related to intestinal glucose absorption and glucose metabolism in mice.

Bisphenol S, an industrial chemical, has raised concerns for both human and ecosystem health. Yet, health hazards posed by bisphenol S (BPS) exposure remain poorly studied. Compared to all tissues, the intestine and the liver are among the most affected by environmental endocrine disruptors. The aim of this study was to investigate the molecular effect of BPS on gene expression implicated in the control of glucose metabolism in the intestine (apelin and its receptor APJ, SGLT1, GLUT2) and in the liver (glycogenolysis and/or gluconeogenesis key enzymes (glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK)) and pro-inflammatory cytokine expression (TNF-α and IL-1ß)). BPS at 25, 50, and 100 µg/kg was administered to mice in water drink for 10 weeks. In the duodenum, BPS exposure reduces significantly mRNA expression of sodium glucose transporter 1 (SGLT1), glucose transporter 2 (GLUT2), apelin, and APJ mRNA. In the liver, BPS exposure increases the expression of G6Pase and PEPCK, but does not affect pro-inflammatory markers. These data suggest that alteration of apelinergic system and glucose transporters expression could contribute to a disruption of intestinal glucose absorption, and that BPS stimulates glycogenolysis and/or gluconeogenesis in the liver. Collectively, we reveal that BPS heightens the risk of metabolic syndrome.

Effects of Bisphenol S on hypothalamic neuropeptides regulating feeding behavior and apelin/APJ system in mice.

Since 2010, Bisphenol A (BPA), an endocrine disruptor has been restricted and replaced by analogues like Bisphenol S (BPS). However, little is known about BPS effects and growing concern have suspected the "BPA-free" Label. Several recent studies suggest that BPS is associated with increased risk of diabetes and obesity. However, the underlying mechanisms remain unidentified. The current study investigates investigate BPS effects on hypothalamic neuropeptides regulating feeding behavior, either orexigenic or anorexigenic in Swiss Albino mice. We also studied the effect of BPS on the apelinergic system (apelin/apelin receptor (APJ)) as an original physiological system with pleiotropic actions. Bisphenol S at 25, 50, 100 µg/kg was administered to mice in water drink for 10 weeks started after weaning. Our results showed that BPS exposure alters orexigenic hypothalamic neuropeptide (AgRP) regulating feeding behavior but not anorexigenic neuropeptides (POMC, CART). Such orexigenic alterations may underlay appetite disorders leading to a concomitant food intake and body weight gain increase. In addition, data show that BPS affects the hypothalamic apelinergic system. We found a significant decrease in APJ mRNA but not in apelin expression. Based on hypothalamic APJ distribution, we suggested a potent specific physiological alteration of this receptor in mediating neuroendocrine responses in hypothalamus. Thus, our findings provide that BPS exposure could contribute to the development of obesity and metabolic disorders.

Peritoneal delivery of sodium pyrophosphate blocks the progression of pre-existing vascular calcification in uremic apolipoprotein-E knockout mice.

Chronic kidney disease (CKD) is generally associated with disturbances of mineral and bone metabolism. They contribute to the development of vascular calcification (VC), a strong, independent predictor of cardiovascular risk. Pyrophosphate (PPi), an endogenous inhibitor of hydroxyapatite formation, has been shown to slow the progression of VC in uremic animals. Since in patients with CKD treatment is usually initiated for already existing calcifications, we aimed to compare the efficacy of PPi therapy with that of the phosphate binder sevelamer, using a uremic apolipoprotein-E knockout mouse model with advanced VCs. After CKD creation or sham surgery, 12-week-old female mice were randomized to one sham group and four CKD groups (n = 18-19/group). Treatment was initiated 8 weeks after left nephrectomy allowing prior VC development. Uremic groups received either intraperitoneal PPi (high dose, 1.65 mg/kg or low dose, 0.33 mg/kg per day), oral sevelamer (3 % in diet), or placebo treatment for 8 weeks. Both intima and media calcifications worsened with time in placebo-treated CKD mice, based on both quantitative image analysis and biochemical measurements. Progression of calcification between 8 and 16 weeks was entirely halted by PPi treatment, as it was by sevelamer treatment. PPi did not induce consistent bone histomorphometry changes. Finally, the beneficial vascular action of PPi probably involved mechanisms different from that of sevelamer. Further studies are needed to gain more precise insight into underlying mechanisms and to see whether PPi administration may also be useful in patients with CKD and VC.

Protective effects of caffeic acid against hypothalamic neuropeptides alterations induced by malathion in rat.

Exposure to pesticides is suspected to cause human health problems. Our study aimed to evaluate preventive effects of caffeic acid (3,4-dihydroxycinnamic acid) in the hypothalamus against malathion-induced neuropeptides gene expression alterations. Malathion at 100 mg/kg was administered intragastrically to rats alone or in combination with caffeic acid at 100 mg/kg during 4 weeks. A molecular expression of hypothalamic neuropeptides and plasmatic cholinesterase activity was investigated. Furthermore, we used in silico analysis, known as computational docking, to highlight the nature of acetylcholinesterase-malathion/caffeic acid interactions. Our findings showed differences in the responses and indicate that caffeic acid reversed malathion-induced decrease in corticotropin-releasing hormone mRNA but not brain-derived neurotrophic factor which presented an increased tendency. We suggest that caffeic acid can interact with acetylcholinesterase as the primary target of organophosphorus compounds. Results predict that caffeic acid can block partly the acetylcholinesterase gorge entrance via π-π stacking interaction with Tyr 124 and Trp 286 residues of the peripheral site leading to its stricture. Under this condition, we suggested that acetylcholine trafficking toward the catalytic site is ameliorated compared to malaoxon according to their sizes.

Bisphenol A and human chronic diseases: current evidences, possible mechanisms, and future perspectives.

Bisphenol-A (BPA) is one of the highest volume chemicals produced worldwide, with over 6billion pounds produced and over 100t released into the atmosphere each year. Recent extensive literature has raised concerns about its possible implication in the etiology of some human chronic diseases such as diabetes, obesity, reproductive disorders, cardiovascular diseases, birth defects, chronic respiratory and kidney diseases and breast cancer. In this review, we present the highlighted evidences on the relationship between BPA exposure and human chronic diseases and we discuss its eventual mechanisms of action, especially genetic, epigenetic and endocrine disruption mechanisms with the possible involvement of oxidative stress, mitochondrial dysfunction and cell signaling.

Effects of pyrophosphate delivery in a peritoneal dialysis solution on bone tissue of apolipoprotein-E knockout mice with chronic kidney disease.

Vascular calcification (VC) is a risk factor for cardiovascular mortality in the setting of chronic kidney disease (CKD). Pyrophosphate (PPi), an endogenous molecule that inhibits hydroxyapatite crystal formation, has been shown to prevent the development of VC in animal models of CKD. However, the possibility of harmful effects of exogenous administration of PPi on bone requires further investigation. To this end, we examined by histomorphometry the bone of CKD mice after intraperitoneal PPi administration. After CKD creation or sham surgery, 10-week-old female apolipoprotein-E knockout (apoE(-/-)) mice were randomized to one non-CKD group or 4 CKD groups (n = 10-35/group) treated with placebo or three distinct doses of PPi, and fed with standard diet. Eight weeks later, the animals were killed. Serum and femurs were sampled. Femurs were processed for bone histomorphometry. Placebo-treated CKD mice had significantly higher values of osteoid volume, osteoid surface and bone formation rate than sham-placebo mice with normal renal function. Slightly higher osteoid values were observed in CKD mice in response to very low PPi dose (OV/BV, O.Th and ObS/BS) and, for one parameter measured, to high PPi dose (O.Th), compared to placebo-treated CKD mice. Treatment with PPi did not modify any other structural parameters. Mineral apposition rates, and other parameters of bone formation and resorption were not significantly different among the treated animal groups or control CKD placebo group. In conclusion, PPi does not appear to be deleterious to bone tissue in apoE(-/-) mice with CKD, although a possible stimulatory PPi effect on osteoid formation may be worth further investigation.

Inhibitors of vascular calcification as potential therapeutic targets.

Vascular calcification is frequent in the general population. Its incidence increases with age. It contributes to cardiovascular morbidity and mortality in patients with advanced atherosclerosis, in the presence or absence of diabetes mellitus and chronic kidney disease (CKD). Both diabetes and CKD aggravate its degree of severity and accelerate its progression. Vascular calcification is the result of both passive and active processes of calcium phosphate deposition in the arterial wall. These processes are more or less successfully opposed by inhibitory proteins and nonpeptidic factors. In the present overview we discuss the roles of several among these vascular calcification inhibitors which represent potential therapeutic targets.

Daily peritoneal administration of sodium pyrophosphate in a dialysis solution prevents the development of vascular calcification in a mouse model of uraemia.

BACKGROUND: The high rate of cardiovascular mortality in patients with end-stage renal disease (ESRD) is a significant barrier to improved life expectancy. Unique in this population is the marked development and aggressive worsening of vascular calcification (VC). Pyrophosphate (PPi), an endogenous molecule, appears to naturally inhibit soft tissue calcification, but may be depressed in chronic kidney disease (CKD) and ESRD. Although once thought to be a promising therapeutic, PPi's very short half-life in circulation curtailed earlier studies. We tested the possibility that a slow, continuous entry of PPi into the circulation and prevention of VC might be achieved by daily peritoneal dialysis (PD). METHODS: Pharmacokinetic studies were first carried out in rats with renal impairment resulting from a 5/6 nephrectomy. Efficacy studies were then performed in the apolipoprotein E gene knockout mouse model overlaid with CKD. PPi was delivered by means of a permanent peritoneal catheter in a solution simulating PD, but without the timed removal of spent dialysate. von Kossa's staining followed by semiquantitative morphological image processing, with separation of inside (intimal) and outside (presumed medial) lesions, was used to determine aortic root calcification. RESULTS: In comparison to an intravenous bolus, delivery of PPi in a PD solution resulted in a slower, extended delivery over >4 h. Next, the efficacy studies showed that a 6-day/week PD-simulated administration of PPi resulted in a dose-dependent inhibition of aortic calcification in both intimal and medial lesions. A dose-response effect on total aortic calcification was also documented, with a full inhibition seen at the highest dose. A limited peritoneal catheter-related inflammation was observed, as expected, and included the placebo-treated control groups. This inflammatory response could have masked a lower level PPi-specific adverse effect, but none was observed. CONCLUSIONS: Our findings suggest potential for PPi, administered during PD, to prevent the development of VC and to potentially extend the life of ESRD patients.

Influence of nitric oxide synthase inhibition on vasopressin and corticosterone secretion during water deprivation in rats.

Nitric oxide (NO) is a short-lived radical that functions as a neurotransmitter in the central nervous system and plays a physiological role in the regulation of hypothalamic-pituitary-adrenal axis and vasopressinergic axis. In the present study, we aimed to investigate the interaction between the generation of NO and vasopressin (AVP) and corticosterone release after 3 days of water deprivation in rats. Animals were previously treated with intraperitoneal (i.p.) saline or L-nitro-arginine methyl ester (L-NAME) injection. L-NAME is a nonspecific inhibitor of nitric oxide synthases. In control rats given i.p. saline or L-NAME, hypothalamic, pituitary, and plasma AVP levels and plasma corticosterone did not change from baseline levels (p>0.05). Three days of water deprivation increased significantly the corticosterone levels in plasma (p<0.01) and AVP levels in hypothalamus and plasma (p<0.01), but not in pituitary, which showed a significant decrease. These variations were concomitant with the elevation of nitrates/nitrates in plasma. L-NAME injection abolished significantly (p<0.01) the elevation of plasma corticosterone and hypothalamic AVP levels induced by water deprivation. These findings showed that in water-deprived rats, nitric oxide synthase inhibition by L-NAME inhibits corticosterone and vasopressin release, suggesting a potent stimulatory role of NO.

Malathion exposure modulates hypothalamic gene expression and induces dyslipedemia in Wistar rats.

Exposure to organophosphate (OP) pesticides is virtually ubiquitous. These inevitable agents are neurotoxicants, but recent evidence also points to lasting effects on carbohydrate metabolism. The aim of this study was to investigate the effects of 32 repeated treatment days with malathion, an OP insecticide, on some molecular and metabolic parameters. Malathion at 100 mg/kg was administered by gavage in Wistar rats. Results of this study indicate a significant decrease in hypothalamic corticotropin-releasing hormone mRNA, of malathion-treated rats. This result, in accordance with that of diabetic type 2 rat model, may be due to very potent negative feedback effects of glucocorticoids on hypothalamo-pituitary-adrenal (HPA) axis activity. In addition, we have recorded a significant increase in hypothalamic inducible NO synthase mRNA which probably enhances the negative feedback. These alterations are accompanied with hypertriglyceridemia that may be a favourable condition to insulin resistance. Thus, results of the present study suggest that malathion can be considered as an important risk factor in the development of diabetes type 2, which prevalence increased substantially in our country and around the world. Clearly, we need to focus further research on the specific incidences of hazardous food chemical contaminant that might be contributing to epidemic health perspectives.

Biochemical evaluation of hepatic damage in subchronic exposure to malathion in rats: effect on superoxide dismutase and catalase activities using native PAGE.

The aim of this study was the evaluation of the hepatic damages following a subchronic exposure to malathion, an organophosphorus (OP) insecticide. Malathion was administered intragastrically in 1 ml corn oil containing 100 mg/kg Body Weight daily for 32 days. Malondialdehyde (MDA) concentration superoxide dismutase (SOD) and catalase (CAT) activities were analysed using a non-denaturing electrophoresis. The serum activities of Pseudocholinesterase (PchE), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were determined. Malathion exposure leads to a significant decrease in AchE activity, an increase in hepatic MDA, and in serum ASAT and ALAT activities. A positive correlation between serum transaminases levels and hepatic MDA was demonstrated. These results indicate that malathion exposure induced lipid peroxidation LPO, a process of degradation of membrane lipids, involving the deterioration of the cellular integrity. We have recorded a slight increase in antioxidant enzymes activities. This leads us to suggest an insufficient elimination of free radicals, causing cytotoxic effects.

Caffeic acid attenuates malathion induced metabolic disruption in rat liver, involvement of acetylcholinesterase activity.

It has been confirmed that organophosphorus compounds OP altered glucose homeostasis. Considerable experimental and clinical evidences have contributed the beneficial effects of polyphenol molecules on metabolic homeostasis. However, up to date limited studies have been performed on this topic. The aim of this study was to evaluate whether caffeic acid, an active phenolic component was able to reduce metabolic disruption induced by malathion administration. Malathion at 100mg/kg was administered to rats alone or in combination with caffeic acid at100 mg/kg. Malathion decreases hepatic GP activity and increases HK activity accompanied with a rise in the hepatic glycogen rate. Moreover, coadministration of malathion with caffeic acid resulted in restoration of malathion-induced GP inhibition and HK1 increase. These results may be due to the significant increase recorded in acetylcholinesterase (AchE) activity in vivo after coadministration of malathion and caffeic acid. Indeed, malathion is known to inhibit AChE activity leads to subsequent activation of cholinergic receptor that increased in part, catecholamine and glucocorticoids secretion; provoked glycogenolysis and gluconeogenesis activation. Thus, we can suggest that increase's (AchE) activity seems to be responsible for caffeic acid restoration on malathion-induced metabolic disruptions. Recent studies support the hypothesis that oxons bind to a secondary site on acetylcholinesterase, leading to activation/inhibition of the catalytic site. Thus, caffeic acid or its derivates may be leading to activation of the catalytic site within the second site interaction.

Effect of subchronic exposure to malathion on metabolic parameters in the rat.

This study investigates the effects of subchronic exposure to organophosphate insecticide Malathion (Fyfanon 50 EC 500 g/l) of commercial grade. It was administered intragastrically by stomach tube in the amount of 1 ml of corn oil containing 100 mg/kg body weight (BW) daily for 32 days. At the end of the experiment, acetylcholinesterase activity (AChE), haematocrit value, haemoglobin content, and blood glucose concentration were estimated. The liver and the skeletal muscle were removed to determine hepatic and muscular glycogen, hepatic proteins and lipids contents. No sign of toxicity was observed until the end of experiment. No significant change in the haematocrit value was observed, in spite of the significant increase in haemoglobin content, which can be considered as an adaptive situation in order to guarantee a good oxygenation in response to pulmonary damage induced following subchronic exposure to organophosphorus compound. Malathion intoxication decreased significantly hepatic proteins and lipid contents that could be associated to liver gluconeogenesis. This result was coupled with a significant decrease in muscular glycogen rate, which indicates a stimulated glycogenolysis in favour of glucose release into the blood until reaching hyperglycaemia. Several studies indicate that hyperglycaemia is temporary, which is probably due to a stimulated glycogenesis that increases hepatic glycogen deposition and return of glucose to control levels, as demonstrated in our study. One possible explanation for these results could be the turnover of glucose by a succession between its release via glycogenolysis and gluconeogenesis, which involves abnormal hyperglycaemia, and its storage via glycogenesis in subchronic exposure to malation.

Effect of subchronic exposure to malathion on glycogen phosphorylase and hexokinase activities in rat liver using native PAGE.

The aim of this study was the evaluation of the effects of a subchronic exposure to malathion, an organophosphorus (OP) insecticide, on plasma glucose and hepatic enzymes of glycogenolysis and glycolysis in rats in vivo. Malathion was administered intragastrically by stomach tube in the amount of 1 ml corn oil containing 100mg/kg body weight (BW) daily for 32 days. At the end of the experiment, the liver was removed. The activities of glycogen phosphorylase (GP) and hexokinase (HK) were analysed in the homogenate. The methodology employed was a non-denaturing electrophoresis followed by activity-staining (native PAGE). Malathion decrease GP activity by 50% and increase HK activity by 10%. In addition, an hepatomegaly was recorded with a rise in the hepatic glycogen rate in malathion-treated rats. Moreover, subchronic administration of malathion has no effect on blood glucose concentration. The storage of glycogen in liver may be due to a stimulation of insulin secretion after the inhibition of acethylcholinesterase activity in pancreatic beta cells by malathion. These findings were in favour of an activation of glycogen storage by malathion.