Inflammatory edema and migration of leucocytes but not phagocytosis are reduced in young rats

RESUMO

1. Newborn and old individuals are more susceptible to infection. In this study vascular permeability as well as the migration of neutrophils and mononuclear cells were determined in male Wistar rats aged 3, 8 and 16 weeks (N = 5-7 animals per group). The increase in vascular permeability induced by the ip injection of carrageenin in 3-week old rats was 2-fold lower than observed for 8- or 16-week old animals. 2. The migration of neutrophils and mononuclear cells into the peritoneal cavity induced by carrageenin and thioglycollate was lower in 3-week old rats (1.4 +/- 0.4 x 10(6) and 1.22 +/- 0.27 x 10(6)) compared to 8-week (4.5 +/- 0.25 x 10(6) and 4.16 +/- 0.38 x 10(6)) and 16-week old animals (5.75 +/- 1.0 x 10(6) and 5.5 +/- 0.5 x 10(6)), respectively. The number of resident cells in the peritoneal cavity of 3-week old rats was also only 15 per cent of that observed for the older rats. The reduced cell migration in younger rats was not the result of leucopenia since the white cell counts of these animals were significantly higher than that of animals aged 8 or 16 weeks (15 +/- 2 x 10(6) vs 8 +/- 1 x 10(6) and 7 +/- 1 x 10(6)/ml of blood, respectively). 3. Although the chemotactic response was lower in 3-week old rats compared to 16-week old animals, the ability of both neutrophils and macrophages from young rats to phagocytose zymosan was similar to that of older animals (60-80 per cent ).(ABSTRACT TRUNCATED AT 250 WORDS)