Local X-irradiation of mouse heart caused a large increase in manganese superoxide dismutase activity (MnSOD) in this organ but not in copper and zinc containing superoxide dismutase (CuZn SOD) activity. MnSOD induction was both dose and time dependent. Another mitochondrial enzyme, citrate synthase, was not induced by X-irradiation. The amount of immunoreactive MnSOD also increased after X-irradiation, showing that the amount of MnSOD protein increased after X-irradiation. The response to X-irradiation was found to be biphasic-with one large peak and one smaller peak of manganese superoxide dismutase activity. The effect of various inhibitors of cellular activities on these two peaks of MnSOD activity was examined. Cycloheximide, a cytosolic protein synthesis inhibitor, abolished both peaks of MnSOD activity, while chloramphenicol, a mitochondrial protein synthesis inhibitor, has no effect on either peak. Actinomycin D, a RNA-synthesis inhibitor, lowered both peaks, but had more of an effect on the second peak than on the first. In vivo protein synthesis studies using [3H]arginine showed that an increase in new protein synthesis occurred during the time period of the second peak, but did not occur during the first peak. These results are consistent with the hypothesis that MnSOD induction occurs in two peaks with the first peak due to a preformed MnSOD protein or mRNA for MnSOD and the second peak due to an increase in new protein synthesis.
|Number of pages||12|
|Journal||Archives of Biochemistry and Biophysics|
|State||Published - Apr 1987|
Bibliographical noteFunding Information:
i This work was supported by a seed grant from the Division of Radiation Therapy, University of Iowa, and NIH Grant lROl-CA41267. ‘To whom correspondence should be addressed at 14 Medical Laboratories, Radiation Research Laboratory, University of Iowa, Iowa City, IA 52242. ’ Present address: Department of Biochemistry, Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, MA 02115. ’ Present address: Pulmonary Research Laboratory, St. Paul’s Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
ASJC Scopus subject areas
- Molecular Biology