A: Relative mRNA expression in mice was determined using qPCR at various developmental stages, as follows : E 17.5, D 0.5 and D 8.5 E: Embryonic day, D: Postnatal day. Results, expressed as the ratio of attomoles of specific gene per femtomole of ribosomal 18S, correspond to mean ± SEM (E17.5 n = 9, D0.5 n = 17, D8.5 n = 6). *** p<0.001. B: Renal 11βHSD2 activity was determined at the same developmental stages and in adults, by measuring the rate of conversion of 3H-cortisol into 3H-cortisone, under three conditions : basal, with NicotinAmid Dinucleotid (NAD), with NAD and carbenoxolone, a specific 11βHSD2 inhibitor. Results, expressed as the ratio of picomoles of enzymatic activity after 2 hours per micrograms of protein, represent the mean ± SEM of three independent experiments for each developmental stage and each condition. * p<0.05; ** p<0.01, NS : Not Significant.