Fig. 6. (A) Western blot analysis of iNOS expression in crude extracts of peritoneal macrophages from mice of the genotypes indicated, 18 h after LPS treatment. Expression of actin is shown as a loading control. (B) Nitrite release in primary cultured murine macrophages from mice of the indicated genotype treated or not with 5 µg/ml LPS for 24 h. Each value represents the mean ± SD of three independent experiments. (C) iNOS expression in crude extracts of splenocytes derived from parp-1^+/+p53^–/– and parp-1^–/–p53^–/– mice.