UBC Theses and Dissertations
Comparative study of post pneumonectomy compensatory lung response in growing male and female rats Singh, Sekhon Harmanjatinder
Male and female Sprague-Dawley rats matched for litter and body weight, were subjected to left pneumonectomy and sham operations at four weeks of age. Three weeks following surgery, rats were sacrificed, and somatic and lung growth, pressure-volume curves, biochemical, and morphometric parameters were measured. Females weighed 48% less than males at the end of the experiment. Somatic growth of neither sex was effected by pneumonectomy. Following pneumonectomy, lung weight and lung volume increased significantly and matched that of both lungs of the sham-operated group in both sexes. The absolute amount of DNA and protein content also increased but was significantly less than that of both lungs of shams. Since females weighed less, absolute lung weight, lung volume, DNA and protein content increased more in males but specific parameters (i. e. values/ 100 g body weight) increased significantly less compared to females. This occurred because specific lung weight and volume decreased with increasing body weight. Mean linear intercept and mean chord length of alveoli were increased. Alveolar surface area increased by 51% in males and 31% in females, and matched that of both lungs of shams in males but not in females. The total number of alveoli increased 15% and 18% in males and females respectively and was significantly less compared to both lungs of shams in both sexes. After pneumonectomy, the post-caval lobe increased in volume 70% and 73% in males and females respectively as compared to a 60% and 47% increase in total lung volume. The mean linear intercept and mean chord length of alveoli increased less in the upper and lower lobes compared to the middle and post-caval lobes in males as well as in females. The number of alveoli per unit volume decreased more in middle and post-caval lobes compared to the upper and lower lobes in both sexes. In sham-operated male rats the upper and lower lobes had a smaller mean linear intercept and mean chord length of alveoli compared to the post-caval lobe. Postpneumonectomy, loss of elastic lung recoil at mid-volumes was observed in females. It was inferred that compensatory response following pneumonectomy was in general similar in males and females. While there was an evidence of alveolar multiplication, simple dilation of airspaces occurred and this was the dominant effect especially in females. In certain aspects (weight, volume) compensatory growth was complete but in most (DNA. protein, morphometry) was not. Male and female differences could not account for differing results in the literature concerning completeness or otherwise of lung compensatory growth.