Neuropeptide-Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) are a family
of 36-amino-acid peptides, which are widely distributed in the body and act through
several subtypes of G-protein-coupled Y receptors. The three members of the NPY-family
peptides are contained in the adrenal gland, where they exert various autocrine/paracrine
regulatory functions. Binding sites for NPY are present in adrenal medulla and zona
glomerulosa (ZG), where also several NPY-ergic fibers end. Binding sites for PYY and
PP are prevalently located in the inner adrenocortical zones and adrenal medulla.
NPY and PYY inhibit aldosterone secretion of dispersed ZG cells, but this effect has
probably to be considered nonspecific and toxic in nature. On the contrary, there
are indications that NPY may indirectly stimulate ZG cells, by eliciting the release
of catecholamines, which in turn enhance aldosterone secretion. Evidence is also available
that NPY modulates the secretory response of ZG cells to their main agonists. PP is
able to raise glucocorticoid secretion acting directly on the inner adrenocortical
cells. The physiological relevance of these effects of NPY-family peptides remains
to be addressed by future experimental studies employing more selective Y receptor
agonists and antagonists. In contrast, indirect evidence is available that endogenous
NPY-family peptides might play an important role in the modulation of adrenocortical
secretory action under paraphysiological or pathological conditions such as like aging,
hypoglycemic stress and pheochromocytomas.
Key words
Neuropeptide-Y - Peptide-YY - Pancreatic Polypeptide - Adrenal Gland - Steroid Secretion
