[The renin-angiotensin system and anterior pituitary function: endocrine interaction or paracrine modulation?]

The identification of elements of the renin-angiotensin system and ulterior demonstration of specific cellular angiotensin II (Ag II) receptors at hypothalamic-pituitary level has suggested the possibility that these peptide play a modulatory role on anterior pituitary secretion. Recent "in vivo" and "in vitro" studies provided confirmation of a stimulatory effect of the renin-angiotensin system on growth hormone (GH) and ACTH variable. Initial experiments indicate that there is no effect on TSH and gonadotrophins secretion. Treatment with angiotensin-converting enzyme inhibitors leads to a reduction of Ag II levels that results in slight decrease of PRL and GH concentrations. However, the mechanism by which Ag II is able to modulate anterior pituitary secretion still remains obscure. Both, indirect effects mediated through changes in neuropeptide secretion or a direct interaction on pituitary cells by a paracrine or endocrine mechanism emerge as possible hypothesis to explain this regulatory function.