E18 fetal rat lung explants were maintained in culture for 24h plus or minus leptin (200 ng/ml), parathyroid hormone-related protein (PTHrP, 5 × 10−7 M), PTHrP plus leptin antibody (PTHrP/LeptinAb) (1:100 dilution), or leptin plus PTHrP receptor antagonist (Leptin/PTHrP Ant., 5 × 10−6 M). Surfactant Protein-B (SP-B) mRNA expression was determined using semi-quantitative RT-PCR as shown in the representative blot. Co-amplification with GAPDH cDNA was used as an internal standard for normalization of the aliquot volumes for leptin mRNA expression. The bars in the graph below the blot represent the mean±standard deviation for control(C) versus treated groups; n=5,***p<.0001 by analysis of variance.