Western blot analyses for retinoid X receptor alpha (RXRalpha), retinoic acid receptor alpha (RARalpha), retinoic acid receptor beta (RARbeta), and retinoic acid receptor gamma (RARgamma) expression in distal lung tissue from mice with and without tobacco toxin exposure during development (TT) at postnatal age P3, P5, and P7. Representative Western blots for RXRalpha (A), RARalpha (C), RARbeta (E), and RARgamma (G). Panels B., D, F, and H: Densitometry analyses of Western blots on distal lung tissue from juvenile mice at postnatal ages P3 with (N = 6) and without (N = 6) TT, P5 (N = 4 each with/without TT), and P7 with (N = 6) and without (N = 5) TT. Compared to tobacco-naïve mice, TT pups expressed significantly decreased RXRalpha at each time point (B): at P3, P = 0.0089, at P5 P = 0.0138, and at P7 P = 0.0227. Decreased expression in the TT mice was also seen for RARalpha, although differences between groups were less than those for RXRalpha, with borderline significance observed at P3 (P = 0.0498) and trends for decreased expression at P5 (P = 0.0709) at P5 and P7 (P = 0.0866) (D). In contrast, TT mice only showed significantly decreased RARbeta at P3 (P < 0.001) (F). The expression of RARgamma was similar to that of RARbeta, with significant decreases seen in the TT mice at P3 (P = 0.0042), with a trend toward decrease at P7 (P = 0.0728). Data comparison performed using Student’s t-test. Abbreviations: RXR = retinoid X receptor, RAR = retinoic acid receptor.