Age and experimental obstructive emphysema. A morphometrical study on the rat

Abstract

Age, as a risk factor in the development of experimental obstructive emphysema, is proposed as the hypothesis of this study. Ninety-two Wistar rats were organized into two age groups: adult (16 weeks) and middle-aged (56 weeks). Each age group was subdivided into three groups: a control group, consisting of unmanipulated animals; a «cannula» group consisting of animals into whose trachea a cannula was implanted; and a «valve» group, consisting of animals into whose trachea a valve had been implanted. The survival was one month. A histomorphometric study was performed on the lungs and the results were compared statistically. 1-hroughout the experiment the amount of food consuni~~byi each animal and the variations in weight were monitored. After sacrifice, the lungs were processed for light microscopy. Thirteen histomorphometric variables were quantified and subsequently systematized into three groups: those which quantified the size of' Iie distal airspace («=ea of the al; ;)!:ir seci .: .,: ,.. , ., . lar chordn and «mean linear interct:l>i . . il~o.,civ hich quantified the tissue («wall tliicknt. - % : : : ,sue density», «interna1 perimeter of eacii ::i\ :c>liii- \c.i,iioii),, <(interna1 alveolar perimeter per fielcl>, ~ i i i ~.,;a lvcolar section/section perimetern); and those which quantified the elastic fibre («elastic fibre area», «elastic fibre perimeter», «elastic fibre area/elastic fibre perimeter», selastic fibre density» and «elastic fibre density per tissue density»). The results were compared statistically and the sensitivity, specificity and misclassification indices were calculated, as well as the attributable and relative risk. From the results, it was observed that, in general, the animals of the valve and cannula groups in both age groups displayed a decrease in food intake and a body weight loss. The middle-aged animals were the only group which displayed significant differences in al1 the morphometric variables except wall thickness, when the cannula and valve groups were compared with the control group. In both the cannula and valve groups, the Offprint [equests to: Dr. Juan de Dios Escolar, Departamento de Ciencias Morfológicas, Facultad de Medicina, 50009 Zaragoza, Spain values of the variables which quantified the distal airspace increased, while the values of the variables which quantified the lung tissue and the elastic fibre decreased. In the manipulated middle-aged group, the attributable risk of developing emphysema was 56.66% and the relative risk 5.55; in the group of manipulated adult animals, the attributable risk was 23.55% and the relative risk 1.66. The results of this study lead us to propose that the middle-aged rats with experimental airflow obstruction displayed a greater risk of developing emphysema than the adult rats which were subjected to the same procedure.