Functional and molecular characterization of VIP receptor-effector system in rat developing immunocompetent cells: G protein involvement

Changes in the functional characteristics for vasoactive intestinal peptide (VIP) receptor-effector system were evaluated in rat developing immunocompetent cells (from 1-week-old animals up to 12-week-old animals). These characteristics include [I-125]VIP binding studies, cell cyclic AMP (cAMP) generation, analysis of [I-125]VIP-receptor complexes by cross-linking experiments, as well as developed-associated G proteins assayed by cholera and pertussis toxin-catalyzed ADP-ribosylation and Western blot. The Scatchard analysis of binding data was consistent with the existence of two classes of VIP binding sites with K-d, values unaltered and B-max increased during postnatal development. The efficiency of VIP stimulation of cAMP generation increased from 1-week-old rats to adult conditions. The VIP-receptor complex apparent molecular mass (52-55 kDa) remains unaltered, but it was significantly lower in 2-week-old than in 8-week-old rats. ADP-ribosylated material by cholera toxin (CTx) was higher from 8-week-old than from 2-week-old animals, while ADP-ribosylation by pertussis toxin (PTx) was quantitatively higher in 8-week-old rats. Results were confirmed when immunoblots for different G protein subunits were performed. (C) 2000 Elsevier Science B.V. All rights reserved.