Brefeldin A and a synthetic peptide to ADP-ribosylation factor (ARF) inhibit regulated exocytosis in melanotrophs.

We investigated the role of ADP-ribosylation factor (ARF) in regulated exocytosis in patch-clamped rat melanotrophs. Addition of brefeldin A (BFA) to inhibit activation of endogenous ARF protein was found to attenuate regulated secretory activity monitored as changes in membrane capacitance (Cm). A synthetic peptide to amino acids 46-61 of ARF (P-14) was also found to inhibit Ca(2+)-induced secretory activity in these cells. This inhibition was not apparent with a scrambled amino acid sequence of ARF-P14 peptide. This paper provides the first patch-clamp study to suggest that the small GTP-binding protein ARF is required to trigger release of secretory granules from rat pituitary melanotrophs.