peptide (PrRP) in both GH3 rat pituitary tumor cells and primary cultures of rat anterior
pituitary cells was investigated. PrRP rapidly and transiently activated extracellular signal-
regulated protein kinase (ERK) in both types of cells. Both pertussis toxin, which inactivates
G i/G o proteins, and exogenous expression of a peptide derived from the carboxyl terminus
of the β-adrenergic receptor kinase I, which specifically blocks signaling mediated by the βγ …