Effect of the protoporphyrinogen oxidase-inhibiting herbicide fomesafen on liver uroporphyrin and heptacarboxylic porphyrin in two mouse strains.

The effect of the protoporphyrinogen oxidase-inhibiting herbicide fomesafen on liver porphyrin accumulation was studied in long-term high-dose experiments. Fomesafen caused liver accumulation of uroporphyrin and heptacarboxylic porphyrin when fed at 0.25% in the diet to male ICR mice for 5 months (fomesafen-treated mice: 52 nmol uroporphyrin, 21 nmol heptacarboxylic porphyrin/g liver; control mice: traces of uroporphyrin, heptacarboxylic porphyrin not detected). Uroporphyrinogen decarboxylase activity was depressed to about 25% of control values. Iron treatment accelerated the development of this porphyria cutanea tarda-like experimental porphyria both in ICR and C57B1/6J mice. In contrast to other uroporphyrinogen decarboxylase inhibitors, fomesafen treatment did not increase the cytochrome P450IA-related activities and the amount of P450IA2 protein was shown to be significantly decreased by Western immunoblotting. Thus, fomesafen is a unique chemical that inhibits both the oxidation of protoporphyrinogen as well as the conversion of uroporphyrinogen to coproporphyrinogen. However, the accumulation of highly carboxylated porphyrins is evident only after prolonged treatment with high doses of the herbicide.

Cord blood levels of potentially neurotoxic pollutants (polychlorinated biphenyls, lead and cadmium) in the areas of Prague (Czech Republic) and Katowice (Poland). Comparison with reference values in The Netherlands. The Czech/Polish/Dutch/German Research Team.

In a preliminary study the levels of four non-planar polychlorinated biphenyls congeners (118, 138, 153 and 180), and of the toxic metals lead and cadmium, and their antagonist selenium and zinc were measured in cord blood from apparently healthy neonates from the region of Prague and Upper Silezia (Katowice). These "background" levels were compared with similar values from neonates in the Netherlands. It was found that the levels of three PCB congeners (138, 153 and 180) were significantly higher in the Prague samples than in the Netherlands; but in the Katowice group they were significantly lower. In Upper Silezia (Katowice) the values of the metals lead and cadmium, and in Prague those of cadmium and selenium were significantly higher than in the Netherlands. The importance of these findings is discussed. It is argued that neurotoxic effects of perinatal exposure can be expected to be more prominent in Central Europe than in Western European countries. A more thorough study is indicated and will be undertaken by a joint Czech/Polish/Dutch/German research group.

[Hepatoma after long-term administration of griseofulvin]. / Hepatom po dlouhodobém podávání griseofulvinu v experimentu.

After the 12- and 14-month administration of the preparation gricin to ten white and two bare (nunu) mice in hepatic tissue in addition to diffuse and nodular hyperplasia hepatomas developed. The ultrastructural changes of tumour cells were not typical and involved above all GER, nuclei and nucleoli. They corresponded to findings of experimental carcinogenesis and human hepatomas.

[Morphological changes in liver tissue in experimental porphyria]. / Morfologické nálezy v jaterni tkáni pri experimentálni porfyrii.

Miscroscopic changes in the liver tissue of mice became detectable 42 hours after the administration of gricine through the appearance of porphyrins in the plasma of hepatocytes marked by the enlargement of their volume, nuclei, and nucleoli. 72 hours after gricine, porphyrins were also found in the lumina of capilary bile ducts and hepatic ducts. This was accompanied by dispersion extinction of hepatocytes and pigment accumulation in the plasma of Kupffer's cells. There was histochemically proved increased activity of alkaline and acidic phosphatase, G6PDH, NADH and NADPH tetrazolium reductase. Under electron microscopy, the porphyrins showed crystalline structure, rotated the plane of polarized light, and were marked by red fluorescence.

The influence of actinomycin D on the activity of delta-aminolaevulinic acid synthetase and dehydratase in the liver of mice and rats treated by griseofulvin.

The changes of delta-aminolaevulinic acid dehydratase--the second enzyme of porphyrin synthesis--were studied and compared in the liver of mice and rats treated with griseofulvin. The results showed that griseofulvin increased the activity of delta-aminolaevulinic acid dehydratase in the liver of mice and rats treated by griseofulvin. No differences were found between mice and rats as to the effect of griseofulvin on the activity of delta-aminolaevulinic acid dehydratase. The influence of the administration of actinomycin D on the activity of delta-aminolaevulinic acid synthetase and dehydratase in the liver of mice and rats was studied at an early period of experimental porphyria induced by griseofulvin. It was found that the administration of actinomycin D blocked the observed effect of griseofulvin on the activity of both enzymes in the liver of mice and rats.

Identification of very-long-chain fatty acids in rat and mouse harderian gland lipids by capillary gas chromatography-mass spectrometry.

Lipids of Harderian ophthalmic gland were separated by means of thin-layer chromatography with flame ionization detection in an latroscan apparatus. Wax ester and polar lipids (phosphatidylethanolamine and phosphatidylcholine) were detected as the main lipids in rats and glyceryl ether diester and both polar lipids were the main lipids in mice. Fatty acids were determined in individual lipid classes by means of gas chromatography and gas chromatography-mass spectrometry on capillary columns. The content of fatty acids, the positional isomers of monoenoic acids being predominantly C18, C20 and C22, is most interesting. Very-long-chain fatty acids, saturated fatty acids up to C30 and even monoenoic acids up to C28 were detected. Branched-chain fatty acids, predominantly iso and anteiso, are minority components, although their chain length distribution (C15-C27) is broad.

Liver high performance liquid chromatographic porphyrin profiles in experimental porphyria induced by peroxidizing herbicides.

The effect of peroxidizing herbicides on the liver porphyrin content of experimental animals was examined. Mice treated with the herbicide oxadiazon accumulated uroporphyrin and protoporphyrin in the liver. Formesafen-treated mice accumulated uroporphyrin and heptacarboxylic porphyrin.

The effect of protoporphyrinogen oxidase inhibitors on microsomal and mitochondrial cytochromes.

Neurological dysfunction is a characteristic feature of acute porphyrias, unexplained until now. One of the possible explanations is a deficiency of heme in the central nervous system, caused by a block in porphyrin biosynthesis. To test this possibility, the content of brain mitochondrial cytochrome a3 was determined after intracerebroventricular administration of the protoporphyrinogen oxidase-inhibiting herbicide fomesafen. It was established in in vitro experiments that fomesafen is a potent inhibitor of brain mitochondrial protoporphyrinogen oxidase (PROTOOX). Addition of 10(-6) M fomesafen to incubation mixture decreased PROTOOX from 1.02 nmol/mg/h (controls) to 0.42 nmol/mg/h. 10(-5)M of fomesafen decreased this activity to 0.27 nmol/mg/h. In in vivo experiments, 5 microleters of fomesafen solution containing 0.2 M fomesafen/l was administered to male rats by intracerebroventricular injection. The content of brain mitochondrial cytochrome a3 was determined 72 hours later. A slight decrease of the a3 content was observed (control rats 0.25 nmol/mg protein, treated rats 0.22 nmol/mg). Brain cytochrome P450 activities were below detection limits in both control and treated groups. In a separate experiment, male ICR mice were fed 1000 ppm of the protoporphyrinogen oxidaseinhibiting herbicide oxadiazon in the diet for 10 days. Liver microsomal cytochrome P450 content was decreased and liver porphyrins increased. An increase of porphyrin content was also observed in the testes of oxadiazon-fed mice, but testicular cytochrome a3 content was unchanged. The results indicate that, contrary to liver microsomal cytochromes P450, the mitochondrial cytochromes are not susceptible to changes in heme biosynthesis.

First demonstration of porphyrins in the lacrimal glands: similarity to the Harderian gland.

The Harderian gland of rodents is the only known tissue with physiological occurrence of high concentrations of porphyrins. In this report we describe the occurrence of considerable concentrations of porphyrins in the extra-orbital and intra-orbital lacrimal glands of the male rat. Similarly as in the Harderian gland, HPLC analysis revealed protoporphyrin as being the prevalent porphyrin homologue in the lacrimal glands. The results may contribute to elucidation of the yet unknown function of the Harderian gland and its porphyrins.

Cobalt inhibition of synthesis and induction of delta-aminolevulinate synthase in liver.

Cobalt has complex actions on the metabolism of heme in the liver. In this organ the metal potently induces heme oxygenase (EC 1.14.99.3), and decreases cellular heme and hemoprotein content. The metal also displays biphasic effects on hepatic heme synthesis. These effects are reflected in the ability of cobalt to initially inhibit synthesis of delta-aminolevulinate synthase [succinyl-CoA:glycine C-succinyltransferase (decarboxylating) EC 2.3.1.37], the rate limiting enzyme of the heme pathway, following which a later enhanced rate of formation of this enzyme occurs. In this study, cobalt was shown to block almost entirely the ability of the barbiturate analogue allylisopropylacetamide to induce delta-aminolevulinate synthase in liver. The blocking effect of cobalt on the otherwise potent enzyme inducing action of this drug was time-dependent; if the metal was injected 30 min prior to allylisopropylacetamide, inhibition of enzyme induction was complete. When the metal was administered 1.5 or more hours after allylisopropylacetamide, inhibition of enzyme induction was incomplete. Cobalt did not block the ability of the drug to directly degrade heme to "green pigment" thus the enzyme inducing action of allylisopropylacetamide and its degradative action on heme are separately mediated.