Receptor expression in cultured PASMCs. (a) Western blot analysis of VPAC-1 and VPAC-2 (and actin as loading control) in PASMCs from controls and PPH patients, showing receptor upregulation, particularly of VPAC-2: lane 1, VPAC-1, control; lane 2, VPAC-1, PPH; lane 3, VPAC-2, control; lane 4, VPAC-2, PPH. (b) Northern blot analysis of VIP receptor expression showing upregulation of both receptor types, which is more marked for VPAC-2: lane 1, VPAC-1, control; lane 2, VPAC-1, PPH; lane 3, VPAC-2, control; lane 4, VPAC-2, PPH. β-actin, control for equal loading of RNA.