钩虾胆碱酯酶（ChE）和谷胱甘肽转硫酶（GST）的敏感性和特异性比较研究

研究了有机磷农药甲地基嘧啶流磷,有机氯农药林丹,菊酯类农药氯菊酯,表面活性剂直链苯磺酸钠和重金属Zn对钩虾（Gammarus pulex L.)胆碱酯酶（ChE）和谷胱甘肽转硫酶（GST）活性变化以及毒性影响,结果表明,在暴露24h和48h后,仅有机磷农药甲基嘧硫磷显著抑制胆碱酯的酶的活性,在暴露48h后,有机氯农药林丹和菊酯类农药氯菊酯能显著提高谷胱甘肽转硫酶活性,在暴露24h后,仅梵在导致谷胱甘肽转硫酶明显升高,作为生物标志物,胆碱酯酶比谷胱甘肽转硫酶具有更高的特异性,这两种生物标志物较毒性试验方法具有更高的敏感性。     

A study of the hepatic microsomal monooxygenase of sea birds and its relationship to organochlorine pollutants

1. The levels of hepatic microsomal monooxygenase in sea birds were determined using organochlorine substrates. Levels of cytochrome P450 and organochlorine residues were also measured. 2. The razorbill (Alca torda) and puffin (Fratercula arctica) showed highly variable activities which were resolved into multiple peaks on frequency diagrams. 3. The most active individuals amongst razorbills were early season females with large ovaries. 4. The properties of monooxygenase from individuals of low and high activity were compared. 5. The results are discussed in relation to PCB pollution.     

Purification and characterization of three forms of glutathione S-transferase A. A comparative study of the major YaYa-, YbYb- and YcYc-containing glutathione S-transferases.

Rat liver glutathione S-transferases have previously been defined by their elution behaviour from DEAE-cellulose and CM-cellulose as M, E, D, C, B, A and AA. These enzymes are dimeric proteins which comprise subunits of mol.wt. 22 000 (Ya), 23 500 (Yb) or 25 000 (Yc). Evidence is presented that YaYa protein, one of two previously described lithocholate-binding proteins which exhibit transferase activity, is an additional enzyme which is not included in the M, E, D, C, B, A and AA nomenclature. We therefore propose that this enzyme is designated transferase YaYa. Transferases YaYa, C, A and AA have molecular weights of 44 000, 47 000, 47 000 and 50 000 respectively and each comprises two subunits of identical size. These enzymes were purified to allow a study of their structural and functional relationships. In addition, transferase A was further resolved into three forms (A1, A2 and A3) which possess identical activities and structures and appear to be the product of a single gene. Transferases YaYa, C, A and AA each had distinct enzymic properties and were inhibited by cholate. The recently proposed proteolytic model, which attributes the presence of multiple forms of glutathione S-transferase activity to partial proteolysis of transferase AA, was tested and shown to be highly improbable. Peptide maps showed significant differences between transferases YaYa, C, A and AA. Immunotitration studies demonstrated that antisera raised against transferases YaYa and C did not precipitate transferase AA.     

A comparative study on the hydroperoxide and thiol specificity of the glutathione peroxidase family and selenoprotein P

Glutathione peroxidase catalyzes the reduction of hydrogen peroxide and organic hydroperoxide by glutathione and functions in the protection of cells against oxidative damage. Glutathione peroxidase exists in several forms that differ in their primary structure and localization. We have also shown that selenoprotein P exhibits a glutathione peroxidase-like activity (Saito, Y., Hayashi, T., Tanaka, A., Watanabe, Y., Suzuki, M., Saito, E., and Takahashi, K. (1999) J. Biol. Chem. 274, 2866-2871). To understand the physiological significance of the diversity among these enzymes, a comparative study on the peroxide substrate specificity of three types of ubiquitous glutathione peroxidase (cellular glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, and extracellular glutathione peroxidase) and of selenoprotein P purified from human origins was done. The specific activities and kinetic parameters against two hydroperoxides (hydrogen peroxide and phosphatidylcholine hydroperoxide) were determined. We next examined the thiol specificity and found that thioredoxin is the preferred electron donor for selenoprotein P. These four enzymes exhibit different peroxide and thiol specificities and collaborate to protect biological molecules from oxidative stress both inside and outside the cells.     

Characterization of the effects of known hepatic monooxygenase inducers on male and female rat and mouse kidneys

Few studies have been designed to quantify the response of the mammalian kidney to agents known to induce monooxygenase activity of renal monooxygenase response to three agents representing different classes of inducers: 2,4,2',4'-tetrachlorobiphenyl (2,4,2',4',-TCB), representative of the barbiturate class, beta-naphthoflavone (BNF), representative of the polycyclic aromatic hydrocarbon class and isosafrole (ISO) as a novel class of inducing agent. Studies were carried out using adult rats and mice of both sexes. Treatment with BNF and ISO stimulated ethoxycoumarin and ethoxyresorufin deethylase activities in renal microsomes from male and female rats and mice, whereas treatment with 2,4,2',4',-TCB had no effect on either enzyme in rats of either sex. NADPH-cytochrome-c-reductase activity was unaffected by any treatment. In rat renal microsomes, cytochromes P-450 and b5 were increased by treatment with BNF and ISO but were not altered by 2,4,2',4'-TCB. Sodium dodecyl sulphate-polyacrylamide gel treated with BNF showed the appearance of a protein band in the 50-60000 dalton range which is similar to that observed in liver microsomes following BNF treatment. These studies confirm and extend previous observations that rat kidney is refractory to induction by inducers of the phenobarbital class, but responds to ISO and the polycyclic aromatic class of inducers. In addition, the studies have demonstrated the presence of a protein in renal microsomes after pretreatment of rats with BNF that was not apparent in microsomes from control rat kidneys.     

Repeated amiodarone exposure in the rat: toxicity and effects on hepatic and extrahepatic monooxygenase activities

Amiodarone is a potent and efficacious antiarrhythmic agent, yet associated with its use are life-threatening pulmonary fibrosis and hepatotoxicity. We have investigated the susceptibility of the male Sprague-Dawley rat to pulmonary and hepatic toxicity after repeated exposure to amiodarone and the effects of such exposure on hepatic and extrahepatic drug metabolizing enzymes. Animals received amiodarone (200 mg.kg-1.day-1 i.p., 5 days/week) for 1 week followed by 150 mg.kg-1.day-1 (5 days/week) for 3 additional weeks. No signs of pulmonary fibrosis or hepatotoxicity were observed, based on histological examination, lung hydroxyproline content, and plasma alanine aminotransferase activity. Analysis of tissues revealed extensive accumulation of amiodarone and desethylamiodarone in lung and liver, but concentrations were significantly lower in animals treated for 4 weeks than for 1 week. In a separate experiment, rats received amiodarone 150 mg.kg-1.day-1 i.p. (5 days/week) for 1 or 4 weeks. No differences in tissue concentrations of amiodarone and desethylamiodarone were detected between animals treated for 1 or 4 weeks. This regimen did not affect hepatic or extrahepatic monooxygenase activities. These results indicate that, in the male Sprague-Dawley rat, there is no observable pulmonary or hepatic toxicity following short-term amiodarone exposure, and there is enhanced elimination of amiodarone and desethylamiodarone when the daily dose of amiodarone is decreased after 1 week from 200 to 150 mg/kg.     

Delayed teratogenic effect of methylmercury on hepatic cytochrome P-450-dependent monooxygenase systems of rats.

Hepatic cytochrome P-450-dependent monooxygenase systems were depressed in adult male rats which had been exposed prenatally to methylmercury. The effect was not seen in immature male or female rats or in adult female rats. This latent teratogenic effect of methylmercury appeared only when exposure occurred during early fetal development. These studies demonstrate that the expression of a chemically induced teratogenic effect may be considerably delayed in the rat and that the stage of development of the fetus at the time of exposure to the chemical agent may be a determining factor.     

A comparative study of the phytotoxic effects of siricid woodwasps on conifers

The effects of siricid mucus and the symbiotic fungus injected artificially, or by oviposition of caged females on young conifer trees were investigated in a comparative study of the phytotoxicity caused by seven species of siricid woodwasps. Dilute solutions of mucus were bioassayed using detached shoots. Rapid physiological changes in the radial growth of the stem, quantity of starch in the leaves, leaf pressure and colour of the foliage of living trees were induced by only one species, Sirex noctilio. Solutions of S. noctilio and S. cyaneus mucus caused premature senescence of needles on detached shoots. The other species, Sirex juvencus, Urocerus gigas, U. augur, U. sah and Xeris spectrum , produced no phytotoxic symptoms in living trees and less rapid senescence of needles on detached shoots. These differences are discussed in relation to the ecology of siricids in the northern hemisphere and the successful establishment of S. noctilio in pine plantations of Australasia.