Effects of chlorinated organics on intermediates in the heme pathway and on uroporphyrinogen decarboxylase.

Experimental porphyria induced by PHAHs is characterized by a progressive reduction in the activity of UROD. After intoxication with TCDD, the most porphyrogenic compound known to date, the liver was the principal site of action, as regards both porphyrin accumulation (mostly uroporphyrin) and the degree of enzyme impairment; the kidney was the site of the second greatest accumulation; the brain and erythrocytes were unaffected. Additional modifications of the heme pathway involved induction of the activity of ALAS and, at least in HCB-induced porphyria after iron pretreatment, may have involved reduced activity of uroporphyrinogen III cosynthetase. These changes can alter the amount and the isomeric composition of uroporphyrinogens and uroporphyrins present in the liver in a way that is likely to help reduce formation of coproporphyrinogen III in porphyric animals. As in the human syndrome porphyria cutanea tarda, iron administration increased porphyrin accumulation and the degree of reduction of UROD activity in mice fed HCB. Mice fed HCB also presented an activation of the type O form of XO. This activation was independent of tissue injury derived from the lipid peroxidation that was concomitant with iron administration. The increase in activity of the type O form of XO may be a characteristic feature of the liver damage found in PHAH intoxication and, in intoxicated animals, could be a source in the liver of oxidant species involved in the mechanism of UROD inactivation--if this inactivation is in fact due to an oxidative reaction.

No evidence of intracellular oxidative stress during ischemia-reperfusion damage in rat liver in vivo.

The role of the intracellular generation of reactive oxygen species in the pathogenesis of ischemia-reperfusion damage of the liver was investigated in two in vivo rat models. Global hepatic ischemia was produced in the left and median lobes for 90 min followed by 60 min reperfusion to the total organ (model A) or only to the ischemic lobes (model B). Although both regimens caused significant rises in serum transaminases, this rise was higher in model B. In neither model was intracellular hydrogen peroxide production nor increased glutathione disulfide in bile found. The activities of various antioxidant enzymes were not affected by ischemia or ischemia-reperfusion. In conclusion, oxygen-free radicals are unlikely to be produced in the cells of rat liver during ischemia-reperfusion.

Investigations on the role of free radical processes in hexachlorobenzene-induced porphyria in mice.

Male C57Bl/10 mice were chronically fed hexachlorobenzene (HCB) (0.02% of the diet) alone or in combination with a single subcutaneous dose of iron (12.5 mg iron per mouse). After eight weeks the group of mice pretreated with the iron overload was highly sensitized to the porphyrogenic effect of HCB, as shown by liver porphyrin accumulation. A synergistic effect of iron was evident on other parameters too, such as HCB-induced hepatic damage, activation of type O of xanthine oxidase, and decreased activity of copper zinc superoxide dismutase and glutathione peroxidase(s). None of these parameters was affected by iron alone. Iron alone and in association with HCB markedly raised the level of lipid peroxides, the increase in the HCB group being smaller. The combined treatment resulted in a significant reduction of HCB's inductive effects on microsomal heme and cytochromes P-450 and b5 and on the activity of aryl hydrocarbon hydroxylase. The content of nonprotein sulfhydryl groups was reduced to the same extent in mice treated with HCB or HCB plus iron. The results suggest that reactive intermediates such as are formed by lipid peroxidation are not sufficient on their own to create the conditions for uroporphyrinogen decarboxylase impairment, as evident in the group of mice receiving iron overload alone. Conversely, HCB administration induced a specific condition of imbalance in the liver between formation and inactivation of reactive intermediates which was associated with hepatic porphyrin accumulation and was potentiated by concomitant administration of iron.

Rapid detection of all HLA-B*27 alleles (B*2701-B*2725) by group-specific polymerase chain reaction.

Human leucocyte antigen-B*27 is strongly associated with a number of rheumatic diseases, including ankylosing spondylitis and reactive arthritis. Targeted detection of the B*27 group by molecular methods is hampered by the extreme heterogeneity of the serological B*27 group. Here, we describe a simple, rapid sequence-specific primer-based method for detection of all 28 B*27 alleles defined to date. The method involves an initial screening with two sequence-specific polymerase chain reactions (PCRs), which has to be followed by two additional PCR amplifications in samples carrying a few rare subtypes of B*27, B*4202 or B*7301. The described protocol should be useful for laboratories involved in diagnostics and research of rheumatoid diseases.