E21 fetal rat lung fibroblasts were cultured in 2 cm2 wells in serum-free DMEM containing 0.1% fatty acid-free bovine serum albumin for up to 6 hours plus or minus parathyroid hormone-related protein (PTHrP, 5 × 10−7 M). Leptin concentrations were determined by an enzyme linked immunosorbent assay for rat leptin. Each bar represents the mean±standard deviation, n=5, *p<.05, **p<.01, ***p<.001 by analysis of variance.