Morphological Changes Accompanying Compensatory Lung Growth After Pneumonectomy in Rats

Abstract

To elucidate morphological change of alveoli in compensatory lung growth, left pneumonecotmy was performed on male 4 weeks-old rats (Fischer-344) and light microscopic morphometry, scanning electron microscopic study and histochemistry using anti-bromodeoxyuridine were made. The wet lung weight and lung volume of the residual lungs in the pneumonectomized rats reached the same as those of sham operated rats at one and two weeks after the operation, respectively. From the data concerning the mean linear intercept in the cardiac lobe of the pneumonectomized rats, alveoli of two different sizes were observed, suggesting that the compensatory lung growth in the alveoli may take two steps or at least two different sizes of alveoli may exist mixed together. The data of histochemistry suggest that in pneumonectomized rats the alveoli beneath the pleura (less than 2mm) included an increased number of S phase cells compared with those of deeper areas. From these morphological changes in the lungs of the pneumonectomized rats it is possible to suggest a hypothesis that stretch stimulation is the first trigger in compensatory lung growth.