AJP - Regulatory, Integrative and Comparative Physiology, Vol 254, Issue 5 755-R760, Copyright © 1988 by American Physiological Society
Development of bronchiolar epithelium: time course of response to oxygen and recovery
G. D. Massaro, L. McCoy and D. Massaro
Pulmonary Research Laboratories, University of Miami School of Medicine, Florida 33136.
Hyperoxia (greater than 95% O2) reversibly suppresses the early postnatal
development of rat bronchiolar epithelium. We now show that blunting of the
normal increase in nuclear numerical density per centimeter cubed of Clara
and ciliated cells becomes apparent within 24 h of exposure to O2 (age 2
days) and reaches a maximum on the last day of hyperoxia (age 7 days). The
intergroup differences began to disappear within 48 h after removal from
O2. During air breathing, Clara cell mitosis increased sixfold between the
ages of 1 and 2 days and returned to day 1 values by age 7 days. During O2
breathing, Clara cell mitosis increased threefold between age 1 and 2 days,
returned to day 1 values by day 4, but exhibited a second peak 24 h post-O2
(day 8) not present in unexposed pups. The onset of differences in the
volume of Clara cell organelles and glycogen was variable, but the
differences were partly or completely eliminated 48 h post-O2 exposure. We
conclude hyperoxia reversibly impairs mitosis by Clara cells.
