Expression levels of LRAT, and CYP26B1 and STRA6 mRNA after treatments with single (PD4) and multiple doses of VA and acidic retinoids. Neonatal rats received an early single dose on PD4 (A-C), or multiple doses on PD4, 7, 11, and 14 (D-F), as described for Figure 1A and C. Quantitative PCR results were normalized to ribosomal 18S RNA and the average value for the control group was set to 1.0 for each experiment. Data are presented as means ± SEM. Each treatment group included n = 4-6 neonates. Statistical analysis was conducted on log10-transformed data using one-factor ANOVA and Fisher’s Least Significant Difference posthoc test. Groups with different letters differed significantly, P < 0.05.