Studies on the effects of L-ascorbic acid on acetaminophen-induced hepatotoxicity. II. An in vivo assessment in mice of the protection afforded by various dosage forms of ascorbate

Hepatocurative and antioxidant profile of HP-1, a polyherbal phytomedicine

HP-1 a herbal formulation comprising of Phyllanthus niruri and extracts of Terminalia belerica, Terminalia chebula, Phyllanthus emblica and Tinospora cordifolia has been evaluated for hepatoprotective activity against carbon tetrachloride (CCl4) induced toxicity. Results show that HP-1 reversed the leakage of lactate dehydrogenase (LDH) and glutamate pyruvate transaminase (GPT) and prevented the depletion of glutathione (GSH) levels in a primary monolayer culture of rat hepatocytes (in vitro). HP-1 attenuated the serum toxicity as manifested in elevated levels of transaminases (glutamate oxaloacetate transaminase (GOT), and GPT) The antioxidative enzymes in liver (catalase and superoxide dismutase (SOD)) were restored to normal values after the oral administration of HP-1. HP-1 suppressed the formation of the superoxide anion radical and reduced CCl4 mediated lipid peroxidation (LPO). Silymarin and antioxidants (ascorbic acid, beta-carotene and alpha-tocopherol) were used for comparison. The present study showed that HP-1 is a potential hepatoprotective formulation with an additional attribute of being anti-peroxidative.

Liver p53 expression in patients with HCV-related chronic hepatitis

Mutated p53 acts as a dominant oncogene and alterations in the p53 gene are described in a large number of patients with hepatocellular carcinoma (HCC). It has been demonstrated that hepatitis C virus (HCV)-core protein regulates transcriptionally cellular genes, as well as cell growth and apoptosis. This study was undertaken to evaluate whether p53 may be expressed also in a precocious stage of HCV-related liver damage. We studied p53 expression by immunoluminometric assay on liver samples from 40 patients (M/F 18/ 22, median age 44 years, range 13-64 years) with biopsy-proven HCV-related chronic hepatitis. We considered the following factors: degree of liver damage, liver iron content and HCV-RNA titre. We also evaluated as possible co-factors alcohol and food intake in the last 3 years. p53 was over-expressed in seven of 40 (17.5%) patients. Liver histology documented the presence of unexpected cirrhosis in two patients among the p53 positive subjects. The p53 positive group had a daily ethanol intake significantly higher in respect to that of the p53 negative group (P < 0.05). Alimentary history documented that patients with a p53 over-expression had a lower intake of total calories, monounsaturated fatty acids, vitamin C and riboflavin. Data indicate that p53 over-expression can occur even in initial stages of HCV-related liver disease.

Gastric emptying in rats with acetaminophen-induced hepatitis

The objective of this work was to study the gastric emptying (GE) of liquids in fasted and sucrose-fed rats with toxic hepatitis induced by acetaminophen. The GE of three test meals (saline, glucose and mayonnaise) was evaluated in Wistar rats. For each meal, the animals were divided into two groups (N = 24 each). Group I was fed a sucrose diet throughout the experiment (66 h) while group II was fasted. Forty-two hours after the start of the experiment, each group was divided into two subgroups (N = 12 each). Subgroup A received a placebo and subgroup B was given acetaminophen (1 g/kg). Twenty-four hours later, the GE of the three test meals was assessed and blood samples were collected to measure the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and acetaminophen. In group IB, the mean AST and ALT values were 515 and 263 IU/l, respectively, while for group IIB they were 4014 and 2472 IU/l, respectively. The mean serum acetaminophen levels were higher in group IIB (120 micrograms/ml) than in group IB (87 micrograms/ml). The gastric retention values were significantly higher in group IIB than in group IIA for all three test meals: saline, 51 vs 35%; glucose, 52 vs 38% and mayonnaise, 51 vs 29% (median values). The correlation between gastric retention and AST levels was significant (P < 0.05) for group IIB for the three test meals: r = 0.73, 0.67 and 0.68 for saline, glucose and mayonnaise, respectively. We conclude that GE is altered in rats with hepatic lesions induced by acetaminophen, and that these alterations may be related to the liver cell necrosis caused by the drug.

Vitamin C in CC14 hepatotoxicity--a preliminary report

1. The hepatotoxic effect of CC14 was studied in the rat by using 3 well established liver function tests (plasma glucose, bilirubin and proteins) as indices of hepatic integrity. 2. The protective effect of vitamin C against this hepatotoxicity was also investigated. 3. CC14 (8 ml kg-1 body weight) caused a decrease in the levels of plasma conjugated bilirubin, glucose and protein. 4. Vitamin C (2 g kg-1 body weight) prevented liver damage induced by CC14. The possible mechanisms of protection are highlighted.

Carbon tetrachloride-induced alterations in hepatic glutathione and ascorbic acid contents in mice fed a diet containing ascorbate esters

The effects of L-ascorbyl stearate and L-ascorbyl palmitate on carbon tetrachloride-induced alterations in glutathione and ascorbic acid content in mouse livers were investigated. Powdered food containing 1% ascorbate ester was given to mice for 3 days before and 1 day after a single injection of CCl4 (0.1 ml/kg, i.p.). Biochemical parameters were determined 1 day after the CCl4 administration. The ascorbate esters markedly attenuated CCl4-induced alterations such as reductions in ascorbate content and hepatic glutathione S-transferase (GST) activity, and increases in glutathione and calcium content and serum GST activity. The CCl4-induced rise in thiobarbituric acid-reactive substances, an index of lipid peroxidation, was not affected by ascorbate feeding. These findings suggest that exogenous ascorbate, in addition to endogenous glutathione, is available to maintain the intracellular milieu in a reduced state, and that this system operates more effectively in aqueous compartments than in membrane lipid bilayers.

Comparison of the effects of ascorbyl palmitate and L-ascorbic acid on paracetamol-induced hepatotoxicity in the mouse

The effects of ascorbyl palmitate (ASCP) and free L-ascorbic acid (LAA) on the hepatotoxicity of paracetamol (acetaminophen) and the in vivo covalent binding of reactive paracetamol metabolites to hepatic proteins has been studied in male MF1 mice. The oral administration of [3H(G)]paracetamol (600 mg/kg) resulted in covalent binding to hepatic proteins, a depletion of hepatic non-protein sulphydryl (NPS) groups after 2 h, and a marked elevation of plasma alanine aminotransferase (ALAT) activity after 24 h. The co-administration of paracetamol and ASCP (1412 mg/kg, equivalent to 600 mg/kg free LAA), but not paracetamol and LAA (600 mg/kg), significantly reduced covalent binding of paracetamol metabolites at 2 and 4 h after treatment. In addition ASCP, but not LAA, significantly reduced the depletion of NPS groups and the elevation of plasma ALAT activity. ASCP also completely prevented the 35% mortality observed at 24 h in paracetamol treated mice. These results demonstrate that ASCP, but not LAA, when co-administered orally with the analgesic is an effective inhibitor of paracetamol-induced hepatotoxicity in the mouse. The mechanism by which ASCP prevents liver injury appears to involve destruction of reactive paracetamol metabolites which is associated with a sparing action on hepatic reduced glutathione levels.

Influence of ascorbic acid esters on acetaminophen-induced hepatotoxicity in mice

Groups of male Swiss-Webster mice were gavaged with acetaminophen (APAP), APAP + ascorbyl stearate (AS), or APAP + ascorbyl palmitate (AP) at a dose of 600 mg/kg for each chemical. APAP alone caused a significant increase in liver weight/body weight ratio and hepatic glutathione (GSH) depletion. Co-administration of the ascorbate esters AP or AS with APAP prevented an increase in liver weight/body weight ratios and hepatic glutathione depletion. APAP + AS treatments caused significantly greater reductions in rectal temperature at 15-30 min post-dosing periods when compared to APAP + AP or AS treatments. Blood levels of APAP had the same relationship. The study indicates a correlation between APAP blood levels and antipyretic effect of APAP + AS and APAP + AP coadministrations. While both ascorbate esters probably afford protection against APAP-induced hepatotoxicity in mice by reducing the reactive intermediate back to the parent compound, the APAP + AS combination provides better therapeutic efficacy as an antipyretic at the 15-30 min post-dosing periods.

Role of calcium in isoproterenol cytotoxicity to cultured myocardial cells

Primary cultures of rat myocardial cells were used to evaluate the cellular dynamics of calcium accumulation after exposure to isoproterenol (ISO). Non-toxic concentrations of ISO (2.4 X 10(-7) M) caused a gradual increase in myocyte calcium uptake. These effects peaked 3 min after exposure and returned to control levels within 2 min. Toxic concentrations of ISO caused a biphasic increase in calcium uptake. The initial phase peaked 1 min after exposure and returned to control levels by 3 min. A second phase was characterized by a progressive increase in calcium uptake that plateaued 10 min after exposure. Ascorbic acid (AA, 5 X 10(-3) M) and sodium bisulfite (SB, 9.6 X 10(-4) M) did not modify the calcium uptake of the initial phase, whereas propranolol (1 X 10(-6) M) and verapamil (1 X 10(-5) M) prevented the initial rise in calcium uptake. In contrast, the antioxidants prevented the the second phase of ISO-induced calcium uptake, whereas verapamil and propranolol did not. The toxic accumulation of calcium induced by ISO may be due to oxidative damage of the sarcolemma. Antioxidants may prevent the formation of oxidative metabolites from ISO and the subsequent calcium overload. Our results show that agents which modify slow calcium-channel transport do not prevent ISO-induced calcium overload in our cell culture system.