LOCAL INFLAMMATORY REACTIONS IN JUVENILE AND ADULT-RATS

The present investigation was designed for the study of the early phas es of local inflammatory reactions in juvenile and adult rats. A recen tly developed experimental model, based on continuous diffusion of an inflammation inducing agent, was applied. Thirty-five juvenile (6 week s) and thirty-five adult (6 months) rats were used. Two sterile teflon tables were implanted subcutaneously on the back of each animal on ea ch side of the midline. After three weeks, when a connective tissue ca psula had developed, the tablets were replaced by one test tablet (con taining lipopolysaccaride) and one fresh teflon tablet, respectively. In each group five animals were sacrificed on day 0 and fifteen animal s on each of day 7 and 21. Biopsies comprising tablet and surrounding tissue were taken and exposed to routine histological treatment. The t otal number of cells was assessed in four defined areas in connection with each tablet. Cells classified as leukocytes were recorded separat ely. The analysis was performed at 1000x magnification in a light micr oscope. During the first seven days an increase in the number of leuko cytes was seen in the tissue adjacent to the test tablets in both youn g and adult rats. After 21 days the number of leukocytes was still hig h in the adult group while in the juvenile group the number of leukocy tes returned to the base-line level.