PULMONARY GRANULAR PNEUMOCYTES Loss of Mitochondrial Granules during Hyperoxia

Hyperoxia is known to injure tissues and cells (1) . In a series of papers the quantitative influence of hyperoxia on some aspects of lung ultrastructure was elucidated (2-4) . These studies revealed that hyperoxia resulted in rapid destruction of the pulmonary capillaries, a thickening of the air-blood barrier, and, eventually, a repopulation of the alveolar epithelium by granular pneumocytes at the expense of the type I alveolar cell . While studying the interrelation between protein synthesis by the lung and the ultrastructure of the pulmonary granular pneumocyte under hyperoxic conditions (5, 6), we noted that the mitochondria of granular pneumocytes from 02-exposed rats seemed to contain fewer granules than those from rats exposed to compressed air . This led to the present study in which we used stereological techniques to examine the influence of in vivo hyperoxia on the dense granule content of mitochondria of rat lung granular pneumocytes .