The histology and collagen content of cotton pellet and polyvinyl sponge-induced granulomas in normal and drug-treated rats.

Comparison of cotton wool and sponge-induced granulomas in the rat showed that collagen contents were very similar despite the different pattern of granuloma formation. There was significantly less variation of individual results in the sponge. Although collagen accounted for less than 10% of the dry weight, there was a positive correlation between the 2 parameters in both models of 9 days but only in the pellet at 15 days. Hydrocortisone treatment significantly decreased dry weight and collagen content. There was rapid cell proliferation and collagen synthesis in the sponge granuloma from Day 5, reaching a peak between the ninth and twelfth day, when DNA levels dropped and collagen increased more slowly to plateau by Day 15. Day 9 was chosen as the most suitable stage to study drug effects. Dexamethasone significantly decreased collagen synthesis whereas indomethacin and phenylbutazone did not. Soluble collagen levels were increased with beta-amino-propionitrile and d-penicillamine; a dose-related effect was obtained with d-penicillamine.