Cell renewal in the lungs of rats exposed to low levels of ozone

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Abstract

This research was undertaken to study the early effects of low levels of ozone on cell renewal in the lungs of rats. To accomplish this, male rats were exposed to ozone for up to 8 days. Dividing cells were labeled with tritiated thymidine ([3H]TdR) and studied with autoradiographic techniques in the light microscope. The results showed that all labeled cells increased and then decreased to near control levels within 4 days. Type 2 cells showed the largest change in labeling index. Since the labeling indexes decreased by the fourth day despite continuous exposure and no further injury occurred, it was assumed the tissue had become tolerant to that concentration of O3. To test the degree of tolerance, groups of animals adapted to O3 were exposed to higher concentrations of O3, and the labeling indexes of Type 2 cells were studied. These studies showed that tolerance to the initial concentration of O3 did not ensure total protection to rats against reexposure to higher concentrations of O3.

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    This research was supported by PHS grants, No. ES 00842 and HL 16330, from the U.S. Department of Health, Education, and Welfare.

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