Agents that increase intracellular cAMP do not reproduce the ET effect on IL-8-driven TEM of PMNs. (A) HMVEC-Ls were treated for 6 h with ET (1000 ng/mL:1000 ng/mL), FSK (10 μM), IBMX (1 mM), or medium alone, and lysed. The lysates were processed for pCREB immunoblotting. To control for protein loading and transfer, blots were stripped and reprobed for β-tubulin. IB, immunoblot, IB*, immunoblot after stripping. (B) The pCREB signals in each blot described in (A) were quantified by densitometry and normalized to β- tubulin signal in the same lane in the same blot. (C) HMVEC-Ls cultured to confluence in assay chambers were treated for 4 h with medium, ET, FSK, or IBMX. These same chambers were then inserted into wells of 24-well plates containing either medium or IL-8 (10 ng/mL), after which calcein-AM-labeled PMNs were added to the upper compartment of each chamber. After 2 h, the contents of each lower compartment were fluorometrically assayed. Each vertical bar represents mean (+/- SEM) TEM of PMNs (%). The n for each group is indicated in each bar. * indicates significantly increased compared to the simultaneous medium controls at p < 0.05. ** indicates significantly decreased compared to IL-8 alone at p < 0.05.