AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1045-R1050, Copyright © 1986 by American Physiological Society
Hyperoxia reversibly suppresses development of bronchiolar epithelium
G. D. Massaro, L. McCoy and D. Massaro
The bronchiolar epithelium of rats is anatomically immature at birth. We
now ask whether postnatal hyperoxia impairs the normal development of
bronchiolar epithelium; and, if development is impaired, is the impairment
permanent? To answer these questions, we exposed newborn rats to hyperoxia
(greater than 95% O2, 1 atm) or air for 7 days and killed the rats at age 7
or 30 days. We used ultrastructural and morphometric means to assess
maturation of the bronchiolar epithelium. Hyperoxia substantially
diminished the postnatal increase in nuclear numerical density of
bronchiolar Clara cells and ciliated cells. Hyperoxia also markedly delayed
the rise in volume density of Clara cell secretory granules and rough
endoplasmic reticulum but accelerated the increase in volume density of
Clara and ciliated cell mitochondria. When rats exposed to hyperoxia from
age 1 to 7 days were thereafter allowed to breathe air, by age 30 days all
the differences were eliminated that were detected between the air- and
O2-breathing groups at age 7 days. We conclude hyperoxia causes a marked
but nonpermanent suppression of maturation of the bronchiolar epithelium.
