A biochemical and morphological study of the cotton pellet granuloma in the rat: effects of dexamethasone and indomethacin (Abstract)

The subcutaneous implantation of a cotton pellet into the rat results in the formation of a granuloma at the site of the implant. The early events comprise an accumulation of fluid and proteinaceous material together with an infiltration of neutrophils. The granuloma formed by day 7 is characterized by the formation of a vascularized fibrous capsule containing fibroblasts, giant cells and infiltrating mononuclear cells. Granuloma development was quantitated by dry weight measurements and its cellular content measured by assaying activity of N-acetyl-B-D-glucosaminidase (NAG) and total nucleic acid content. Nucleic acid determinations and histological examination show that cell infiltration into the granuloma takes place at a virtually constant rate over a 7 day period. In contrast the NAG activity does not change significantly until after day 5 when a large increase in the amount of enzyme extractable from the granuloma is seen. Systemic treatment of the animal with dexamethasone or indomethacin results in an inhibition of granuloma weight gain, NAG activity and nucleic acid levels. Drug treatment on days 0–3 results in suppression of granuloma formation whereas treatment on days 4–7 is without affect. This suggests that the two drugs are acting during the early phases of granuloma development. Histological examination shows clear differences between the action of dexamethasone and indomethacin.