Biochemical & histochemical changes relating to fibrosis following infection with Mycobacterium tuberculosis in the guinea pig.

ABSTRACT

Guinea pigs infected with M. tuberculosis were studied for parameters relating to fibrosis following infection. The infected animals were followed up to a period of 44 wk and the changes that occurred in the lung, liver and spleen were studied. Corresponding tissues from animals injected with bleomycin, an anti-mitotic drug which has the ability to produce pulmonary fibrosis, served as positive controls. Tissue collagen, elastin and hexosamines were estimated biochemically. The presence of granuloma and stainable collagen in paraffin sections of these tissues was also studied. Establishment of the infection was assessed bacteriologically by culturing the viable organisms from the spleen. It was observed that a self-limiting infection was established in the guinea pigs and none of the animals died of the infection. In the infected animals, collagen, elastin and hexosamines showed an initial decrease followed by an increase. While the elastin and the hexosamine levels returned to the basal levels in all the three organs, collagen levels increased in the lung and were comparable to those of the bleomycin control. Collagen stainable by Van Gieson's method was found to be increased in the lung from the 4th wk onwards. The present report indicates the potential of adopting this system for studying mechanisms of fibrogenesis in tuberculous infection.