Angiotensin II receptors induce tyrosine dephosphorylation in rat fetal membranes

CIUFFO GM; ALVAREZ SE; FUENTES LB

REGULATORY PEPTIDES

ELSEVIER SCIENCE BV

Año: 1998 p. 129 - 135

0167-0115

Recently, it has become clear that many of the intracellular signals mediated by Ang II receptors are similar to the signaling pathways activated by receptor tyrosine kinases. In the present paper, we are reporting a full characterization of Ang II receptors in rat fetal 125 1 8 125 membranes. We assayed binding of the Ang II antagonist [ I]Sar Ile Ang II and the AT specific competitor [ 1]CGP42112. Both 2 ligands exhibited a rapid equilibrium and a high specificity for Ang II receptors. Competition studies confirmed the presence of both receptor subtypes, with a predominance of AT receptors and the following order of potency: CGP42112-Ang II-Losartan-PD123177. Immunoblotting studies of tyrosine phosphoproteins showed that Ang II (10 M) mediates a rapid reduction in tyrosine phosphorylation of several proteins with apparent molecular masses in the range of 30–45 kDa. Increasing concentrations of Ang II  showed a dose–response behavior, suggesting a clear physiological role of the observed effect. The response, blocked by Losartan and PD123177, seems to be mediated by both receptor subtypes. These results clearly indicate that both Ang II receptors mediate tyrosine dephosphorylation in early stages of development and support a role of these receptors in growth and development.