Stimulation of RBP4 mRNA and protein expression by cAMP and HMGA1. (Upper left) 20 μg of total RNA from Hepa1 cells treated with the indicated concentrations of Br-cAMP for 24 h (lanes 1–7) were analysed by Northern blot. Hybridization was carried out with an RBP4 cDNA or an 18S RNA probe as a control of the RNA loaded on each lane. (Lower left) 20 μg of total RNA from Hepa1 cells treated with 0.5 mM Br-cAMP for the indicated times were loaded on each lane (lanes 1–8) and analysed as above. (Right) Hepa1 cells, in the absence or presence of an expression plasmid (1 μg) containing the HMGA1 cDNA in either the sense (s) or antisense (as) orientation, were left untreated or treated with Br-cAMP (0.5 mM), total protein extracts were prepared 48 h later and HMGA1 and RBP4 protein expression levels were detected by Western blot (WB) with anti-HMGA1 and anti-RBP4 antibodies, respectively. β-actin, control of cellular protein loading. Densitometric analyses of three to five independent blots are shown.