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The effects of some xenobiotics on the activity of the B6-dependent kynurenine hydrolase (KH) and kynurenine aminotransferase (KATE) in mouse liver, were investigated. Polychlorinated biphenyl (Aroclor 1254) (400mg/kg/day x4) markedly decreased the activity of both enzymes. Benzo(a)pyrene (BP) and 3-methylcholanthrene (3-MC) (40mg/Kg/day x1) as well as phenobarbital (PB) (75mg/kg/day x3) did not alter the activity of KH, while that of KATE was mildy reduced. The response of the two enzymes to treatment with chlorpromazine (CPZ) (5mg/Kg/day x5) were opposite with marked elevation of KH and inhibition of KATE activities. Treatment with B-naphthoflavone (B-NF) (80mg/Kg/day x2), Pyrazole (200mg/Kg/day x1) or indole (400mg/kg/day x1) produce no change in the activity of either enzyme. It, seems therefore, that Aroclor (1254) and chlorpromazine may cause disordered kynurenine metabolism through alterations in the activities of its metabolizing enzymes. This, in turn, might affect nicotinamide adenine dinucleotide biosynthesis and/or the accumulation of some tryptophan metabolites suspected of being carcinogenic or co-carcinogenic.

The interrelationship between pyridoxal phosphate and gonadotropin and thyroxine in their effects on kynurenine metabolism was studied in the whole liver homogenates from male mice. These in vitro studies were planned to investigate the effects of these hormones on the vitamin B6-dependent enzymes, kynurenine aminotransferase and kynurenine hydrolase. It was found that gonadotropin (from serum of pregnant mares) inhibits both enzymes, whereas thyroxine inhibits the kynurenine aminotransaminase enzymes only. There was evidence indicating that pyridoxal phosphate was not the factor directly responsible for the observed inhibition. Increasing concentrations of pyridoxal phosphate were unable to counteract the inhibitory effects of these hormones.

The effectiveness of E. coli and bovine liver beta-glucuronidases in the hydrolysis of the urinary beta-glucosiduronides of tryptophan metabolites was studied. Some of these metabolites demonstrate carcinogenic activity in the mouse bladder. Moreover, the effect of the prolonged contact of these conjugates to the urinary enzyme was investigated in the first and second voiding urine samples. The former urine was that retained in the bladder during sleep (about 8 hours) and the latter was collected 3 hours after the first. It is found that both enzymes have no important role in releasing the free carcinogens from their glucosiduronides. The presence of free carcinogens could be attributed to the spontaneous hydrolysis of some labile conjugates. However, the prolonged contact of the freely active substances during the sleeping hours with the epithelium of the bladder may enhance the process of bladder carcinogenicity. The increased accumulation of these metabolites in the first voiding urine could be interpreted in terms of their rate of excretion rather than by the enzymatic hydrolysis of their conjugates.

The effectiveness of Escherichia coli and bovine liver beta-glucuronidases in the hydrolysis of the urinary beta-glucosiduronides of tryptophan metabolites was studied. Moreover, the effect of the prolonged contact of these conjugates to the urinary enzyme was investigated in the first and second voiding urine samples. It is found that both enzymes have no important role in releasing the free carcinogens from their glucosiduronides. The presence of free carcinogens could be attributed to the spontaneous hydrolysis of some labile conjugates. However, the prolonged contact of the freely active substances during the sleeping hours with the epithelium of the bladder may enhance the process of bladder carcinogenicity. The increased accumulation of these metabolites in the first voiding urine could be interpreted in terms of their rate of excretion rather than by the enzymatic hydrolysis of their conjugates.

The present work is an up-to-date approach to study the correlation between the excretion pattern of tryptophan metabolites along the kynurenine pathway (after loading with 2 gm. L-tryptophan), and the N-nitrosamine content in urine of bilharzial bladder cancer patients. The control group was composed of healthy subjects who had no reported history of S. haematobium infection and no current bacterial cystitis. The N-nitrosamine content was determined by the colorimetric method of Eisebrand and Preussmann (1970). It was demonstrated that 64 per cent of the patients metabolized the tryptophan load abnormally and the others metabolized it almost normally. Moreover, the N-nitrosamines were present in 43 per cent of controls and 93 per cent of patients have these derivatives in higher values. The presence of an inverse correlation between certain tryptophan metabolites, shown previously to be bladder carcinogens, and the N-nitrosamine content, especially after loading, was interpreted in view of the possible conversion of some tryptophan metabolites into N-nitrosamines either under endovesical conditions or during the execution of the colorimetric determination of these compounds. Therefore, thorough investigation is urgently needed to study the origin of these urinary N-nitrosamines. Moreover, improved method(s) for their colorimetric determination are also urgently needed.

In the present study use was made of the chelating ability of EDTA and the activating property of some metal ions Ca(II), Mg(II) or Mn(II) to counteract the inhibitory effect of Cu(II), Co(II), Pb(II) or Zn(II) ions on the B6-dependent kynurenine hydrolase and on kynurenine aminotransferase. These may be of help in studying the therapeutic trials in the treatment of metal poisoning. EDTA was able to counteract the inhibitory effect of Cu(II) or Co(II) on kynurenine aminotransferase and partially counteract the inhibitory effect of Cu(II), Co(II) on kynurenine aminotransferase and partially counteract the inhibitory effect of Cu(II), Co(II), Pb(II) or Zn(II) ions on kynurenine hydrolase. The difference in the response of the two B6-dependent enzymes to EDTA is attributed to the difference in the functional groups involved in the active site(s) of the two apoenzymes. Moreover, Mn(II), Ca(II) and Mg(II) ions have the ability to counteract some of the inhibitory effect of these metal ions.

The effect of 5 consecutive daily i.p. doses of CPZ (5 mg/kg), PZ (10 mg/kg) and PMZ (10 mg/kg) on the activity of kynurenine hydrolase and kynurenine aminotransferase in mouse liver was studied. All three phenothiazines effected an increase in the activity of kynurenine hydrolase per unit weight of liver with CPZ showing the highest activation followed by PZ and PMZ. On the other hand kynurenine aminotransferase was more moderately inhibited by the above treatment. In vitro studies showed that the phenothiazines tested and the pharmacologically inactive CPZO, the major metabolite of CPZ, in concentrations ranging from 3 X 10(-9) to 3 X 10(-4) M had an activating effect on kynurenine hydrolase. Increases in activity were obtained up to concentrations of 3 X 10(-6) M and levelled off afterwards. The highest increases were observed with CPZ and CPZO, while those of PZ and PMZ were of lesser magnitude. However, the tested phenothiazines were without effect on kynurenine aminotransferase. The newly introduced psychotropic drug, sulpiride, which is a substituted benzamide, was devoid of activity on either enzyme both in vivo (50 mg/kg) and in vitro (3 X 10(-9) to 3 X 10(-4) M).

High values of anthranilic acid, 3-OH-kynurenine, xanthurenic acid and 3-OH-anthranilic acid are observed in the spontaneous urinary excretion of tryptophan metabolites in girls in the prepubertal age. The highest differences are between the 3-hydroxy metabolites especially the 3-hydroxykynurenine. On the other hand, this metabolic excretion in postmenopausal women is statistically identical to that of women in sexual maturity.

We have studied tryptophan metabolism "via kynurenine" in women who were oral contraceptives users, living in two different egyptian environments: in the city of Alexandria or in a rural area near Tanta and, in comparison, in control groups of women living in the same environments but who were not contraceptives users. In the non contraceptives users of Tanta we have registered a higher elimination of some metabolites (anthranilic acid, kynurenic acid, xanthurenic acid and 3-OH-anthranilic acid) which might be related to the way of life and environment. The pattern of the kynurenine pathway metabolites of the contraceptives users (studied 1, 3 and 12 months after contraceptives administration) shows some differences with respect to the controls, both in the spontaneous elimination and in that after tryptophan load. These differences are especially evident for anthranilic acid glucuronide, kynurenine and kynurenic, anthranilic and xanthurenic acids. Some differences may be observed after 1 month of contraceptives administration. The effect of tryptophan oral load is superimposed on those of environment and contraceptives use; in the spontaneous elimination of tryptophan metabolites an accomodation to the contraceptives administration is evident. The discrepancies between some of our results and those of the literature might be related to the influence of environmental factors and of the way of life.

Serum alkaline ribonuclease activity and serum albumin concentration were determined in 25 normal children and 59 children with protein-energy malnutrition. The increase in serum ribonuclease was marked in marasmus and marasmic kwashiorkor. The ribonuclease activity dropped significantly after two weeks of treatment and returned to normal by four weeks. In kwashiorkor, serum ribonuclease activity was significantly lower than control and returned to normal after four weeks of treatment. These findings support previous observations that the serum ribonuclease is a good criterion of the nutritional status and indicates that the enzyme activity, particularly when related to serum albumin, is a good prognostic index in this respect.

The conversion in vitro of kynurenine into kynurenic acid and anthranilic acid in both normal kidneys and those obtained from mice infested with Schistosoma mansoni was investigated. Normal mouse kidneys seem to possess an excess of functional pyridoxal phosphate over those obtained from infested mice. Kynureninase and kynurenine transaminase in the latter kidneys are more easily inhibited by deoxypyridoxal phosphate and tartar emetic, indicating low stores of active pyridoxal phosphate. The possible implication of these findings in relation to the role of the kidneys in producing abnormal patterns of tryptophan metabolism and possibly contributing to the production of bladder tumours in bilharzial patients is discussed.