Effects of 100% oxygen on cell division in lung alveoli of squirrel monkeys

The purpose of this study was to determine the effects of 100% oxygen on cell division in lung alveoli of squirrel monkeys. To accomplish this, squirrel monkeys were exposed to 100% oxygen for up to 5 d. Prior to sacrifice, cells preparing to divide were labeled with tritiated thymidine (3H-Tdr). Labeled cells were visualized with autoradiographic techniques, counted with the light microscope, and expressed in terms of a labeling index. In the present study it was shown that DNA synthesis was initially inhibited by exposure to 100% oxygen. However, within 3 d it was returning to normal and by 5 d was well above control levels. Analysis of the cell types involved showed that the large increase in labeling was due to an increase in dividing Type 2 cells, which is thought to be for replacement of damaged Type 1 cells.