In an attempt to establish which RNA polymerase catalyzes the synthesis of the low molecular weight RNA components A, C and D, Ama 1 cells (mutant Chinese hamster cells) were used in experiments with addition of alpha-amanitin. Ama 1 cells contain an altered RNA polymerase II which is 800 times more resistant towards inhibition by alpha-amanitin than the wild type enzyme. Alpha-amanitin (up to 200 microgram/ml) added to these cells does not affect the synthesis of the low molecular weight RNAs A, C and D. These data together with our previous data showing that alpha-amanitin (0.5 - 5.0 microgram/ml) preferentially inhibits the synthesis of A, C and D in normal cells indicate that RNA polymerase II catalyzes the synthesis of the low molecular weight RNA components A, C and D.
The mono-ortho-substituted polychlorinated PCB congener 2,3',4,4',5'-pentachlorobiphenyl (PCB-118) was administered i.p. (30 mg/kg body weight) to gonadally immature rainbow trout (Oncorhynchus mykiss), of both sexes. In liver microsomes prepared from fish killed 4 days after administration, the cytochrome P450-dependent monooxygenase activities of 7-ethoxyresorufin O-deethylase (EROD), aryl hydrocarbon hydroxylase (AHH), and aldrin epoxidase (AE) were measured. In addition, NADPH-cytochrome c reductase (NCCR) was analyzed, and the content of a specific cytochrome P450 isozyme was determined with Western blotting and an enzyme-linked immunosorbent assay (ELISA) using rabbit anticod P450IA1 IgG. The monooxygenase parameters EROD and AHH were significantly induced to 558 and 268%, respectively, of the corresponding control values, while NCCR and AE activities were not affected. The antibodies to cod P450IA1 recognized a single protein band (Mr = 58,000 D) in the rainbow trout liver microsomes. The ELISA absorbance of this protein in the PCB-118 treated fish was 401% of the corresponding value in the controls. These results demonstrate that PCB-118 is an effective inducer of the subfamily cytochrome P450IA1 in rainbow trout liver microsomes.
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