[Angiotensin II and its effects on vascular structure].

The peptide vasoconstrictor angiotensin II (Ang II), originally described as deriving exclusively from the plasma renin angiotensin system, has now been demonstrated to be produced independently of such sources. Local tissue angiotensin-generating systems are well documented. There is increasing evidence that these locally produced vasoconstrictor peptides may contribute to blood vessel homeostasis, as well as the development of vascular pathologies. Results obtained from pharmaceutical intervention in these systems in humans and animals strongly support this hypothesis. In addition to its vasoconstrictor properties, Ang II acts as a potent biological effector. In vitro both vasoconstrictor peptides appear to modulate the activity of autocrine feedback loops in vascular smooth muscle cells. The activity of these feedback loops in vivo may represent a central mechanism for regulation and phenotypic differentiation of this cell type. The most well-established autocrine feedback loops of vascular smooth muscle cells are constituted by platelet-derived growth factor and transforming growth factor-beta, both of which are influenced by the action of angiotensin II. The effects of the peptide vasoconstrictors on the (auto) regulated feedback loops are of long-term structural importance since both vasoconstrictors (via autocrine growth modulators) may influence the composition of the extracellular matrix of vascular smooth muscle cells. This includes effects on the synthesis and secretion of thrombospondin, fibronectin, tenascin, etc.(ABSTRACT TRUNCATED AT 250 WORDS)