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Serum prealbumin concentrations have been studied, by a quantitative immunological procedure, in patients with secondary carcinoma of the liver, chronic active hepatitis, alcoholic hepatitis, cryptogenic cirrhosis, obstructive jaundice, inflammatory bowel disease, and myocardial infarction. The results showed that prealbumin concentration is significantly decreased when liver function is impaired. In diseases not associated with liver damage the concentrations of prealbumin were within the normal range. The advantage of this biochemical procedure is that serum prealbumin concentration is a true index of liver function, whereas serum enzyme activities signify only the degree of hepatocellular damage, which may not always quantitatively reflect liver function. Determination of serum prealbumin is therefore valuable in the diagnosis of liver disease and in the monitoring of treatment.

Hepatocyte nodules, a characteristic early step in the development of liver cancer in rats, has a distinctive resistance phenotype including a large decrease in total cytochromes P-450 and in two isozymes induced by phenobarbital and two by 3-methylcholanthrene. In this study, it has been observed that the nodules show a large decrease in an additional cytochrome P-450, cytochrome P-452, which is very active in the hydroxylation of lauric acid at C-11 and C-12. The decrease in activity of this microsomal cytochrome P-452 is of the same order of magnitude as the decreases in the other cytochrome P-450 components. These observations are consistent with the hypothesis that there is some more basic alteration in the synthesis or availability of heme and that the changes in the activities of the cytochromes P-450 are secondary.

The effect of dietary substitution of starch by sucrose, glucose, fructose or an equimolar mixture of glucose and fructose on the activity of biphenyl hydroxylase and the level of the major terminal mixed function oxygenase, cytochrome P-450, has been studied in hepatic microsomal preparations from growing rats. The substitution of sucrose for starch depressed the concentration and total activity per liver of biphenyl 4-hydroxylase and the concentration, but not the total amount, of cytochrome P-450 in weanling rats. The absolute amount of these enzymes in whole liver was not, however, similarly depressed by the constituents of sucrose, namely glucose and fructose, either when given alone or in equimolar mixture. All these sugars, however, depressed the total activity of biphenyl 2-hydroxylase. The activity of biphenyl 4-hydroxylase in the liver of weanling rats, but not of adults, was reduced when the level of sucrose in the diet was reduced from 60 to 10 %.

The various classes of toxic chemicals that may be present in food namely environmental contaminants, natural toxins, pesticide residues, food additives and contaminants, are reviewed. It is emphasized that the real hazards from toxic chemicals in food are the result of gross contamination, deliberate or accidental, and a number of such incidents are briefly described.

A gas-liquid chromatographic method for the determination of feprazone in various biological matrixes, employing a choice of detector options, is described. After rapid, micro-scale extraction of the sample with n-butyl acetate at physiological pH, the solution was injected directly onto the chromatograph. Separation was with either an OV7 column and flame ionisation or electron capture detection, or with a carbowax high polymer column and nitrogen specific detection. When 100 microl of plasma was extracted the limit of accurate measurement was 2 mg 1(-1) for F.I.D. and N.P.D. and 0.5 mg 1(-1) with E.C. detection. Quantification was by comparison with a range of plasma calibrators carried throughout the procedure, and determination of peak height ratios against an internal standard incorporated into the extracting solvent. The CV of the assay throughout the concentration range normally encountered in patients undergoing feprazone treatment, ranged between 2.4 and 7.8% for the various detector options. The analytical method has been applied to samples collected both from patients and normal volunteers undergoing treatment with a range of feprazone maintenance doses.

Pretreatment of young rats and mice with certain drugs and polycyclic hydrocarbons stimulates the hydroxylation of biphenyl by liver microsomal preparations. Phenobarbitone, nikethamide and meprobamate, all increase the 4-hydroxylation of biphenyl but have little effect on the 2-hydroxylation. In contrast, the carcinogenic polycyclic hydrocarbons, 3,4-benzpyrene, 20-methylcholanthrene, and 1, 2, 5, 6-dibenzanthracene preferentially stimulate the 2-hydroxylation of biphenyl. Non-carcinogenic polycyclic hydrocarbons such as 1, 2, 6, 7-dibenzpyrene and 2, 3, 6, 7-dibenzanthracene stimulate neither mode of hydroxylation. Biphenyl is metabolized in vivo into 4-hydroxybiphenyl (20 per cent of the dose in rats, 25 per cent in mice) and 2-hydroxybiphenyl (2 per cent in rats, 5.5 per cent in mice). Pretreatment with phenobarbitone produces moderate stimulation of the 4-hydroxylation in rats, but not mice: 2-hydroxylation is unaffected. Pretreatment with benzpyrene produces stimulation of 2-hydroxylation in both species, but does not affect the 4-hydroxylation. It is suggested that a correlation may exist between the carcinogenicity of polycyclic hydrocarbons and their induction of the hepatic microsomal enzyme responsible for the 2-hydroxylation of biphenyl.

Dehydroacetic acid (DHA) labeled with C14 in four carbon atoms has been synthesized. DHA administered orally to rabbits at a dose level of 250 mg/kg did not increase the urinary excretion of glucuronides or ethereal sulfates. Small oral doses (20–70 mg/kg) of C14-DHA were not rapidly excreted. In 3–7 days rabbits excreted 70–80% of the dose in the urine, 7–10% in respiratory CO2, and 2–3% in the feces; 8–17% remained in the tissues. In 4–5 days, rats excreted 20–40% in the urine, 10–25% in respiratory CO2, and 10–20% in the feces; 5–26% remained in the tissues. In both rats and rabbits the highest radioactivity was found in the blood. Electrophoresis of human serum incubated with C14-DHA showed that DHA is mainly associated with serum albumin and to a lesser extent with serum globulins. Three metabolites of DHA have been isolated from rabbit urine: triacetic acid lactone (TAL); a hydroxy-DHA, probably 3-glycoloyl-6-methyl-2,3-dihydropyran-2,4-dione; and metabolite X, which is probably the salt of triacetic acid lactone 3-carboxylic acid. A further metabolite, compound Y, which is not a pyrone but probably a degradation product of DHA, was detected. DHA and hydroxy-DHA react with ammonium salts to form the corresponding 1′-imino derivative, imino-DHA and imino-hydroxy-DHA. After administration of DHA to rats and rabbits, the DHA and hydroxy-DHA occur in the urine partly free and partly as the imino derivatives. The urines of rabbits receiving small oral doses of C14-DHA contain an average of DHA (total) 5% of the dose, hydroxy-DHA (total) 20%, TAL 10%, urea 0.3%; metabolites X and Y were estimated to account for 20 and 15%, respectively. Similarly, rat urines contain DHA (total) 5%, hydroxy-DHA (total) 8%, TAL 1%, and urea 0.3%. At higher dose levels the percentages of dose excreted as DHA and hydroxy-DHA are markedly increased, and the percentages as metabolites X and Y markedly decreased. 2,6-Dimethyl-4-pyrone and its 3-carboxylic acid, deoxydehydroacetic acid; orcinol; malonic, succinic, oxalic, and acetic acids; and acetone were shown not to be urinary metabolites of DHA. DHA and hydroxy-DHA, but not TAL, were found in the feces and gut contents of rats after subcutaneous injection of DHA, suggesting that these two compounds are excreted in the bile. The pattern of excretion of metabolites after injection of DHA did not differ significantly from that following oral administration. C14-DHA was metabolized by rat liver, but not kidney, to hydroxy-DHA, TAL, and CO2. A pathway for the metabolism of DHA via hydroxy-DHA, compound X, TAL, and triacetic acid to acetoacetic acid and CO2 is suggested. Because of the reactivity of the keto group of the acetyl side chain and the tendency of DHA and hydroxy-DHA to combine with the amino groups of proteins and other essential compounds, the administration of DHA might have serious deleterious effects. The ultraviolet absorption spectra, color reactions, and chromatographic behavior of the metabolites of DHA and a number of other pyrones are given.

Administration of a single dose of the inhibitor of the hepatic mixed function oxidases, 9-hydroxyellipticine (9-OHE), resulted in a marked increase in the cytochrome P-448 catalysed activities of ethoxyresorufin O-deethylase, biphenyl 2-hydroxylase and activation of benzo[a]pyrene to mutagens. In contrast there was no effect on the cytochrome P-450 catalysed benzphetamine N-demethylase activity. The inductive effect was prevented by simultaneous administration of the protein synthesis inhibitors cycloheximide and actinomycin D. It is concluded that 9-OHE may also act as an inducer of the hepatic microsomal mixed function oxidases, selectively inducing the synthesis of cytochrome P-448. Therefore, 9-OHE, like other inhibitors of this enzyme system, exhibits a biphasic effect, its inhibitory phase being followed by one of enzyme induction. 9-OHE was a direct mutagen in the Salmonella typhimurium strains TA 98 and TA 100.

Three groups of 24-day-old male Wistar rats were fed (a) a control diet containing 210 g/kg protein ad libitum (control) (b) a low protein diet consisting of the stock diet diluted with starch to contain 70 g/kg protein ad libitum (protein deficient) or (c) an amount of stock diet containing the same amount of protein as eaten by (b) but without starch (energy deficient). The low protein diet did not affect the ability of the animals to metabolize biphenyl and excrete it as 4-hydroxybiphenyl, or reduce the total activity of 4-hydroxylase per liver, whereas this was reduced by restricted amounts of the high protein diet. The low protein diet resulted in raised levels of corticosteroids in the plasma. It is concluded that the raised specific activity, and unchanged total amount of biphenyl 4-hydroxylase per liver of the low protein animals is an adaptation to the diet mediated by corticosteroids as exogenous corticosteroids were also found to increase the activity of this enzyme in normal animals.

The serum activity of glycylprolyl-p-nitroanilidase (GPN) has been compared with isocitrate dehydrogenase and with alanine and aspartate aminotransferases in patients with hepatobiliary diseases, myocardial infarction and chronic inflammatory bowel disease. Serum GPN was markedly increased in all hepatobiliary diseases, especially secondary carcinoma and chronic alcoholic hepatitis, but no abnormal values were seen in patients with chronic inflammatory bowel disease. Slightly elevated GPN activities were noticed in a few cases of myocardial infarction. It is suggested that serum GPN would be useful for monitoring hepatic function, especially in the clinical trials of new drugs.

The activities of the drug metabolizing enzymes biphenyl-4-hydroxylase, p-nitrobenzoate reductase, 4-methyl umbelliferone glucuronyl transferase and the amounts of cytochrome P-450, DNA and microsomal protein have been determined at 6,12,18 and 21 days in the livers of rats reared from birth in large (15 pups) and small (3 pups) litters. Undernutrition retarded the gain in liver weight more than that of body weight during the first 12 days. It did not, however, change the concentration per unit weight of liver of any of the constituents measured. Phenobarbital did not change the body or liver weight in either group, but increased the amount of microsomal protein at 12 days and doubled the amount of DNA per 100 g body weight in both groups at 12 and 21 days. The percentage increase in enzyme activity caused by phenobarbitone was greater in the undernourished animals than in the controls.

Triacetic acid lactone (TAL) labeled with C 14 in three carbon atoms has been synthesized. The C 14 of small oral doses of C 14 -TAL fed to rats (250–350 mg/kg) and rabbits (50–60 mg/kg) was mostly excreted in the expired air and urine within 24 hours. In 3 days, rats excreted 45–50% in the respiratory CO 2 , 20% in the urine, and 7% in the feces; 10–20% remained in the tissues. Rabbits, in about the same period, excreted 50–60% as CO 2 , 30% in the urine, and 4% in the feces; 10–20% remained in the tissues. With both rats and rabbits most of the radioactivity in the urine occurs as unchanged TAL (13–25% of dose) together with small amount of urea (2–11% of dose). In the urines of rabbits only, a third unidentified metabolite accounting for 10% of the dose, and probably a degradation product of TAL, was detected. Paper chromatography did not reveal the presence of DHA, hydroxy-DHA, or compound X in the urines of rats or rabbits dosed with C 14 -TAL. C 14 -TAL is more rapidly oxidized to CO 2 by rat kidney slices than by liver slices. DHA, hydroxy-DHA, and compound X were not detected as in vitro metabolites of TAL. Unlike DHA, TAL does not appear to combine with tissue proteins.

HEOD labelled with 14C was administered to CFE rats and CF1 mice and the excreted radioactivity was examined to characterize the various HEOD metabolites. In addition to the pentachloroketone and 9-hydroxy metabolites, the identities of two further metabolites of HEOD in the rat were established. These are a faecal metabolite, 6,7-trans-dihydroaldrindiol, and a urinary metabolite, the hexachlorohexahydromethanoindene-dicarboxylic acid, which may be formed by oxidation of the diol. Three of the rat metabolites, but not the pentachloroketone, were found in the excreta of the CF1 mouse. Where possible the quantity of radio-activity present as any given metabolite was determined. A sample of the new urinary metabolite of the rat was synthesized and shown to have an acute oral toxicity of >850 mg/kg in the CF1 mouse. Prior induction of enzyme activity appeared to affect the production of urinary metabolites of HEOD in the CFE rat but not in the CF1 mouse.