Further investigations on the effects of neuropeptide Y on the secretion and growth of rat adrenal zona glomerulosa.
NPY is a regulatory peptide, high levels of which are contained in adrenal glands of several mammals and which is co-released with catecholamines during various stressful conditions. The acute and chronic effects of NPY on adrenocortical secretion and growth were studied in the rat. NPY concentration-dependently increased aldosterone (ALDO), but not corticosterone (B) secretion of adrenal slices (maximal effective concentration was 10(-7) M). Two competitive inhibitors of NPY receptors, named PYX-1 and PYX-2, were found to dose-dependently inhibit ALDO response of adrenal preparations to 10(-7) M NPY; PYX-2 was more efficient than PYX-1, and at a concentration of 10(-5) M completely annulled the effect of 10(-7) M NPY. The acute bolus intraperitoneal (i.p.) injection of NPY (3 nmol/kg) raised plasma ALDO concentration (PAC), but not that of B (PBC); this effect of NPY was blocked by the simultaneous injection of PYX-2 (300 nmol/kg). The prolonged i.p. infusion with NPY (3 nmol/kg/h for 7 days) increased PAC (but not PBC) and induced a marked hypertrophy of the zona glomerulosa (ZG) and its parenchymal cells; dispersed ZG cells obtained from NPY-infused rats displayed a significantly enhanced basal and maximally agonist-stimulated ALDO production. The simultaneous infusion with PYX-2 (300 nmol/kg/h) completely annulled all these effects of NPY. The acute or chronic administration of PYX-2 alone did not evoke any apparent effect on the ZG secretion and growth. In light of these findings the following conclusions can be drawn: (i) NPY is able to stimulate not only the secretion, but also the growth of adrenal ZG in rats, via a receptor-mediated mechanism (since this effect is blocked by PYX-2); (ii) endogenous NPY does not play a prominent role in the physiological maintenance of secretion and growth of rat ZG (since PYX-2 alone is ineffective); (iii) NPY may play a crucial role in the fine tuning of the ZG functions in conditions requiring an increased release of mineralocorticoid hormones.
Mazzocchi
G
G
Department of Anatomy, University of Padua, Italy.
Malendowicz
L K
LK
Macchi
C
C
Gottardo
G
G
Nussdorfer
G G
GG
D000450:Aldosterone / Q000097:blood / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D003345:Corticosterone / Q000097:blood / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009478:Neuropeptide Y / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017476:Receptors, Neuropeptide Y / Q000037:antagonists & inhibitors; D015384:Zona Glomerulosa / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*
D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; D000450:Aldosterone; D003345:Corticosterone