Adaptive lung growth during chronic cold plus hypoxia is age-dependent.

Abstract

AbstractWealing male guinea pigs (Cavia porcellus) of initial body weight 207–271 g and 2–3 weeks of age were exposed for up to 16 weeks to combined cold (Ta = 6°C) and hypoxia (ambinet P = 85 torr) before analysis (range of body weights at sacrifice, 253–932 g). The body growth rate of the cold + hypoxia guinea pigs was not different from that of the control animals raised at Ta = 22°C and an ambient P = 133 torr. After 3 weeks of cold + hypoxia exposure, and a mean body weight of 402 g, the weight‐specifi lung volume, VL, of 3.59 ± 0.29 ml/100 g BW (mean ± SEM) in cold + hypoxia was significantly greater than the value of 2.65 ± 0.16 for age‐ and weight‐matched controls. However, by week 16 of exposure, there wer no significant differences in VL betweent he experimentals (2.24 ± 0.08) and the controls (2.04 ± 0.15). Similar relationships were found between the two groups for weight‐specific alveolar epithelial and capillary endothelial surface areas. Although chronic exposure to both increased oxidative demand and reduced oxygen availability trasiently increased the pulmonary dimensions suitable for gas exchange, normal adult dimensions were ultimately achieved. Furthermore, the similarity of lung growth in cold plus hypoxia to the patterns reported for exposure to cold or hypoxia alone suggests a common and rather nonspecific response mechanism for such adaptive growth in the lung.