Biochemical changes associated with the potentiation of acetaminophen hepatotoxicity by brief anesthesia with diethyl ether.

Acetaminophen hepatotoxicity in male CD-1 mice was enhanced markedly by brief anesthesia with diethyl ether (ether), and particularly so if acetaminophen was given several hours after ether. The present study was conducted to examine the possible biochemical mechanisms behind this delayed toxicologic synergism. In vitro biochemical studies indicated that ether anesthesia produced a delayed reduction in the activities of glucuronyl transferase and glutathione (GSH) S-transferase, and in the hepatic content of GSH. The hepatic content but not activity of the cytochromes P-450 was initially reduced by ether but recovered by the time of maximal toxicologic enhancement. In vivo studies showed that ether produced a small decrease in the plasma concentrations of glucuronide and sulfate conjugates of acetaminophen, with a concomitant, minor increase in the half-life of acetaminophen, and a major increase in the bioactivation of acetaminophen, as determined by an early, 2-fold increase in the plasma GSH and cysteine conjugates of acetaminophen, and a 3-fold increase in the covalent binding of acetaminophen to hepatocellular protein. Decreases produced by ether in the in vivo production of acetaminophen glucuronide correlated with increasing plasma concentrations of unmetabolised acetaminophen, decreasing hepatic GSH content and increasing covalent binding of acetaminophen to hepatocellular protein when these measurements were performed in the same animals. The biochemical mechanisms underlying the potentiation of acetaminophen hepatoxicity as measured by plasma glutamic pyruvic transaminase concentrations appeared to be due to delayed, complex effects of ether upon multiple enzymatic pathways of acetaminophen elimination and detoxification.

Location of motoneurons innervating the middle ear muscle of the chicken, (Gallus domesticus).

The motoneuron pool for the musculus columellae, the avian equivalent to the m. stapedius, was identified by retrograde labeling with WGA-HRP. It consists of a discrete group of approximately 65 neurons located along the dorsolateral border in the ventral subnucleus of the facial nuclear complex. Other facial motoneurons were only labeled when diffusion of the tracer into neighbor structures was not excluded. The dorsal subnucleus of the facial nerve innervates the m. depressor mandibulae.

Effect of diethyl ether on the bioactivation, detoxification, and hepatotoxicity of acetaminophen in vitro and in vivo.

Our working hypothesis for designing this study involved early inhibition by ether of P-450-dependent bioactivation and glucuronyl transferase-dependent "detoxification", with an earlier recovery of bioactivation. The combined in vivo and in vitro results from the same animals indicate that the increased susceptibility to acetaminophen hepatotoxicity may have been due to a combination of delayed decreases induced by ether in the activities of glucuronyl transferase, sulfotransferase and GSH S-transferase, along with a depletion of hepatic GSH. The small decrease in hepatic content of cytochromes P-450 at 2 hr when toxicologic enhancement was minimal, together with repletion at 8 hr when enhancement was maximal, while the above detoxification pathways were inhibited, is compatible with our hypothesis. However, the lack of an accompanying change in the activity of P-450 suggests either that a different P-450 isoenzyme is involved, or that P-450 activity was not toxicologically limiting. The toxicological imbalance in the bioactivation and detoxification of acetaminophen observed after ether pretreatment was evidenced by significant increases both in the plasma concentrations of GSH and cysteine conjugates, and in the covalent binding of acetaminophen to hepatocellular protein.

Repetitive microvolumetric sampling and analysis of acetaminophen and its toxicologically relevant metabolites in murine plasma and urine using high performance liquid chromatography.

Acetaminophen is a widely used, nonprescription analgesic and antipyretic drug which can cause severe hepatic and renal cellular necrosis. Analysis of plasma and urinary concentrations of acetaminophen metabolites can facilitate an understanding of the relation of enzymatic pathways involved in the bioactivation and detoxification of acetaminophen to its cellular toxicity. There is a marked interindividual variability in the activity of these enzymatic pathways which play a critical role in the modulation of acetaminophen toxicity. A similar interindividual variability occurs in the in vivo temporal disposition of acetaminophen and its metabolites. Accordingly, optimal in vivo methods would permit repetitive sampling from the same animals, as opposed to sacrificing groups of different animals for each time point. This is particularly difficult in smaller rodents such as the mouse, where generally a single blood sample is obtained by cardiac puncture, often under conditions of general anesthesia which can affect drug metabolism and toxicity. A microvolumetric technique for repetitive blood sampling in individual mice, combined with a simple, high performance liquid chromatographic assay for acetaminophen and its toxicologically relevant metabolites is reported here. Data are presented for the disposition of acetaminophen and its metabolites in murine plasma, feces, and urine.

Potassium sorbate dip as a method of extending shelf life and inhibiting the growth of Salmonella and Staphylococcus aureus on fresh, whole broilers.

In two separate plant studies, the refrigerated shelf life of fresh whole broilers at 3 C was extended by dipping freshly chilled carcasses in a 5% (w/w) solution of potassium sorbate for 1 min. After 7 days, control birds had odor and slime formation and psychrotrophic counts of greater than 10(7)/cm2. Sorbate treated birds showed no spoilage until the 14th or 15th days. Dipping in sorbate also reduced the growth of Salmonella and Staphylococcus aureus inoculated onto the broiler carcasses. This study confirmed earlier findings that sorbate is effective in controlling growth of spoilage organisms associated with fresh poultry.

Murine acetaminophen hepatotoxicity: temporal interanimal variability in plasma glutamic-pyruvic transaminase profiles and relation to in vivo chemical covalent binding.

The hepatotoxicity of acetaminophen is thought to be dependent upon its enzymatic bioactivation to a reactive intermediary metabolite which binds covalently to essential cellular macromolecules, thereby causing cellular death. Traditional in vivo methods using smaller mammals are mechanistically restrictive in that measures of hepatotoxicity, such as plasma glutamic-pyruvic transaminase (GPT), and chemical covalent binding to hepatocellular protein are performed at different times in separate groups of animals. We developed a microanalytical technique which allowed repetitive plasma GPT sampling from individual mice, followed by delayed determination of covalent binding in the same mouse 36 hr after acetaminophen administration. Diethyl ether anesthesia was used to enhance acetaminophen hepatotoxicity. The repetitive sampling technique permitted an accurate determination of the peak GPT concentration, which exhibited a marked interanimal variability in the time of occurrence. Individual peak GPT concentrations correlated with the respective covalent binding of acetaminophen in each mouse (r = 0.82, p less than 0.05), while the traditional method using a fixed sampling time (24 hr) failed to correlate (r = 0.50, p greater than 0.05). Ether produced a 39-fold enhancement in the severity of acetaminophen hepatotoxicity; however, a single, fixed-time sample taken at either 12 or 24 hr produced a substantial and inconsistent over- or underestimate of this toxicologic enhancement. This study shows that chemical hepatotoxicity as reflected by plasma GPT concentration cannot be quantified accurately by a single blood sample obtained from a given animal, regardless of the chosen sampling time.(ABSTRACT TRUNCATED AT 250 WORDS)