Young Hamsters Are More Resistant than Adults to Endotracheally Instilled Porcine Pancreatic Elastase

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Abstract
We measured the physiologic and stereologic response to 0.1, 0.2, and 0.4 .mu.g of porcine pancreatic elastase instilled in a volume of 0.25 ml 0.9% NaCl/100 g body weight into the trachea of groups of young and adult hamsters. The young hamsters averaged 50 g and the adult hamsters 116 g in initial body weight. Twenty-one days after administration of elastase, lung volumes, static lung compliance, maximum expiratory flow, the whole section mean linear intercepts (MLI) were measured. The degree of emphysema increased in all animals as a function of dose. Examination of the lung volume and compliance dose-response characteristics indicated that young hamsters developed less physiologic change with increasing elastase dose than did adult hamsters. Maximum expiratory flow and whole section MLI dose-response were similar in the young and adult elastase-treated groups. However, the MLI in young hamsters treated with the 0.4 .mu.g elastase dose was decreased in the outer third of the lung compared to adult emphysematous hamsters. Also, mean airspace density relative to saline control values in young hamsters was double that found in adult hamsters treated with the 0.4 .mu.g elastase dose. Although serum alpha1-globulin levels were equivalent in both young and adult normal hamsters, values normalized for lung elastin content were significantly increased in young animals. We conclude that young hamsters show less change in lung function as a function of elastase dose twenty-one days after elastase instillation. Possible reasons for this include an increased ratio of lung alpha1-globulin/lung elastin in young hamsters, their continued ability to grow new alveoli, and age related differences in airway size favoring a central distribution of enzyme.