Expression levels of STRA6, LRAT, and CYP26B1 mRNA after multiple doses of VA and VA combined with different mole percentages of acidic retinoids. Neonatal rats were treated with on muliple doses on PD4, 7, 11, and 14. An equal amount of VA, equivalent to 6 mg retinol/kg was given either alone or combined with varying proportions of RA or Am580, from 10% to 1% compared to VA. Gene expression levels were determined for STRA6 (A), LRAT (B), and CYP26B1 (C) 6 h after the final dose. 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 ± EM with values for individual neonates shown as symbols. 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.