Prieto Jc

Interaction of vasoactive intestinal peptide with human blood mononuclear cells.

The binding of vasoactive intestinal peptide (VIP) and the stimulation of adenylate cyclase were studied in mononuclear cells from human peripheral blood. The binding depended on time, temperature and pH, and was reversible, saturable and specific. Binding studies suggested the presence of 2 classes of binding site: a class with high affinity (Kd = 2.4 X 10(-10)M) and low capacity (8 fmoles/10(6) cells), and a class with low affinity (Kd = 8.0 X 10(-8)M) and high capacity (800 fmoles/10(6) cells) at 15 degrees C. Secretin displaced [125I]VIP from the cells with a 400-fold lower affinity than VIP, but glucagon, somatostatin and insulin did not show any effect. VIP was a potent and efficient stimulator of cyclic AMP production. The stimulation was observed at a concentration as low as 3 X 10(-11)M and depended on time, temperature and pH. Maximal cyclic AMP production (4-fold above basal levels) was observed with 10(-9) M at 15 degrees. Half-maximal response was obtained at 10(-10)M VIP. Secretin was an agonist of VIP but exhibited a 7000 times lower potency. Peripheral blood mononuclear cells constitute an easily accessible and suitable system for the study of VIP action in different physiological and pathophysiological conditions.

Activation of cyclic AMP-dependent protein kinase by VIP in blood mononuclear cells.

Vasoactive intestinal peptide stimulated cyclic AMP-dependent protein kinase activity in human blood mononuclear cells. The simultaneous presence of a phosphodiesterase inhibitor was required to elicit maximal activation. The apparent Ka value of half the maximal stimulation was about 60 pmol. Secretin exhibited a 170-times lower potency. Other peptides such as glucagon or insulin had no effect even at 1 microM.

Interaction of vasoactive intestinal peptide with a cell line (HeLa) derived from human carcinoma of the cervix: Binding to specific sites and stimulation of adenylate cyclase

SummaryThe binding of vasoactive intestinal peptide (VIP) and its effect on cyclic AMP production were assessed in HeLa cells. The binding of [125I]VIP is a moderately rapid process, reversible, saturable, specific and dependent on temperature. Virtually no inactivation of the peptide is observed after 2 h of exposure to the cells. At 15°C, the binding data obtained at steady state are compatible with the existence of two classes of binding sites: a first class with a Kd of 2.4nM and low binding capacity (1.5×105 sites/cell) and a second class with a Kd of 100 nM and a high binding capacity (4.9×106 sites/cell). Secretin is eight times less potent than VIP in competing with125I VIP but glucagon, insulin and somatostatin are inactive. VIP-induced stimulation of cyclic AMP production depends on time and temperature and is potentiated by a phosphodiesterase inhibitor. A concentration of VIP as low as 10−10M is able to stimulate adenylate cyclase. Half-maximal stimulation is observed at 10−9M and maximal stimulation (4 times above basal levels) at 10−8 M VIP. Secretin is an agonist of VIP but exhibits a 1000 times lower potency with respect to adenylate cyclase activation. Glucagon, insulin and somatostatin do not show any effect. The presence of high-affinity binding sites and the high sensitivity and specificity of adenylate cyclase for VIP in HeLa cells provide a good model to study the role of this peptide on cell proliferation and differentiation.

Interaction of vasoactive intestinal peptide with Hela cells: Activation of cyclic AMP-dependent protein kinase and lack of effect on DNA synthesis

Abstract Vasoactive intestinal peptide (VIP) stimulated protein kinase activity in HeLa cells. Maximal activation by the peptide required the simultaneous presence of a phosphodiesterase inhibitor. The response was dose-dependent in the 0.3–10 nM range, half-maximal stimulation being observed at 1 nM VIP. This value agrees with the concentration of VIP required for half-maximal stimulation of cyclic AMP production as well as with the Kd of the high affinity binding sites for VIP in the same cell system (15). Secretin also stimulated protein kinase activity but with a 300-times lower potency than VIP. When DNA synthesis in Hela cells was studied, no effect of VIP could be seen in a 0.1–100 nM range of peptide concentration.