Protein Kinase C Mediates the Contractile Actions of Pituitary Adenylate Cyclase Activating Polypeptide in Guinea Pig Gallbladder Strips

Pituitary adenylate cyclase activating polypeptide (PACAP) was shown to relax guinea pig gallbladder strips contracted with cholecystokinin. This relaxation was mediated by PACAP interacting with VIP/PACAP receptors. PACAP was also shown to cause contraction in guinea pig gallbladder strips. The present study demonstrated that calphostin C and bisindolylmaleimide IV, both blockers of protein kinase C, significantly reduced tension, Rp-adenosine 3', 5'-cyclic monophosphatase triethylamine, a blocker of protein kinase A, had no effect on PACAP-induced tension. Nifedipine also significantly reduced the PACAP effect. The contractile effects of PACAP are mediated by protein kinase C.