Phospholipase-induced modulation of rat liver mixed-function oxidase activity

1999 ◽  
Vol 27 (4) ◽  
pp. 371-374 ◽  
Author(s):  
C. E. Rolph ◽  
P. Roberts ◽  
S. Taylor
Keyword(s):  
Rat Liver ◽  
Oxidase Activity ◽  
Mixed Function Oxidase ◽  
Mixed Function Oxidase Activity

scholarly journals Growth hormone and drug metabolism. Acute effects on microsomal mixed-function oxidase activities in rat liver

1976 ◽  
Vol 154 (2) ◽  
pp. 433-438 ◽  
Author(s):  
J T. Wilson ◽  
T C. Spelsberg
Keyword(s):  
Growth Hormone ◽  
Drug Metabolism ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Male Rats ◽  
Mixed Function Oxidase ◽  
Liver Growth ◽  
Mixed Function Oxidases ◽  
Cytochrome P 450 ◽  
Mixed Function Oxidase Activity

Adult male rats were subjected either to sham operation or to hypophysectomy and adrenalectomy and maintained for a total of 10 days before treatment with growth hormone. Results of the early effects of growth hormone on the activities of the mixed-function oxidases in rat liver over a 96h period after growth-hormone treatment are presented. 2. Hypophysectomy and adrenalectomy result in decreased body and liver weight and decreased drug metabolism (mixed-function oxidases). Concentrations of electron-transport-system components are also decreased. 3. In the hypophysectomized/adrenalectomized rats, growth hormone decreases the activities of the liver mixed-function oxidases and the cytochrome P-450 and cytochrome c reductases, as well as decreasing the concentration of cytochrome P-450 compared with that of control rats. Similar but less dramatic results are obtained with sham-operated rats. 4. It is concluded that whereas growth hormone enhances liver growth, including induction of many enzyme activities, it results in a decrease in mixed-function oxidase activity. Apparently, mixed-function oxidase activity decreases in liver when growth (mitogenesis) increases.

scholarly journals The effects of carbon disulphide on rat liver microsomal mixed-function oxidases, in vivo and in vitro

1980 ◽  
Vol 188 (1) ◽  
pp. 107-112 ◽  
Author(s):  
Maria J. Obrebska ◽  
Peter Kentish ◽  
Dennis V. Parke
Keyword(s):  
Rat Liver ◽  
Oxidase Activity ◽  
Carbon Disulphide ◽  
Intraperitoneal Administration ◽  
Male Rats ◽  
Type I ◽  
Mixed Function Oxidase ◽  
Mixed Function Oxidases ◽  
Cytochrome P 450 ◽  
Mixed Function Oxidase Activity

An intraperitoneal dose of CS2 (500mg/kg) to male rats resulted in loss of liver microsomal mixed-function-oxidase activity (85% loss of biphenyl 4-hydroxylase), followed by denaturation of liver cytochrome P-450 to cytochrome P-420, and degradative loss of both cytochromes (50% loss). Losses of NADPH–cytochrome c reductase (20%) and cytochrome b5 were considerably less. Intraperitoneal administration of CS2 (100mg/kg) to rats pretreated wtih phenobarbitone or 3-methylcholanthrene resulted in similar losses, but the rate of destruction was greater with cytochrome P-450 than with cytochrome P-448. At 12h after intraperitoneal injection of CS2 to non-pretreated rats, a new cytochrome (P-448) appeared. Rat liver microsomal preparations incubated with CS2 in the presence of NADPH and O2 resulted in loss of cytochrome P-450 and mixed-function-oxidase activity directly related to the concentration of CS2 (10–100μm) and to the period of incubation. Addition of EDTA (1mm) completely inhibited this destruction of cytochrome P-450 by CS2in vitro. Addition of CS2 to liver microsomal preparations resulted in moderate increases in the Ks values for type-I or type-II substrates, but these were insufficient to account for the inhibition of the mixed-function oxidases. We therefore suggest that desulphuration of CS2 leads to binding of the S to cytochrome P-450, denaturation of cytochrome P-450 to cytochrome P-420, and ultimately to destruction of these cytochromes by autoxidation.

PYRETHROID RESISTANCE IN PEAR PSYLLA, PSYLLA PYRICOLA FOERSTER (HOMOPTERA: PSYLLIDAE), AND SYNERGISM OF PYRETHROIDS WITH PIPERONYL BUTOXIDE

1989 ◽  
Vol 121 (3) ◽  
pp. 219-223 ◽  
Author(s):  
Everett C. Burts ◽  
Hugo E. van de Baan ◽  
Brian A. Croft
Keyword(s):  
Oxidase Activity ◽  
Pyrethroid Resistance ◽  
Cyano Group ◽  
Piperonyl Butoxide ◽  
Mixed Function Oxidase ◽  
Pear Psylla ◽  
Mixed Function Oxidase Activity

AbstractAdult pear psylla, Psylla pyricola Foerster, from commercial pear orchards near Wenatchee, WA, were tested using a slide-dip technique for susceptibility to fenvalerate over a 5-year period from 1984 to 1988. Results were compared with those from similar tests using psyllids from an unexposed population near Corvallis, OR. During 5 years, resistance of adults to fenvalerate increased by 16- to 32-fold at Wenatchee while that of the Corvallis population did not change. In 1988, tests with five pyrethroids and pyrethroid – piperonyl butoxide combinations indicated that pear psylla adults also were resistant to permethrin and flucythrinate but not to fenpropathrin or cyfluthrin which contain a cyano group that reduces their susceptibility to oxidase metabolism. Piperonyl butoxide synergism was proportional to the level of resistance, indicating that resistance is probably due to increased mixed function oxidase activity. Implications of this study to control of post-diapause winter form adults in commercial pear orchards is discussed.

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