Neuropeptide K enhances glucocorticoid release by acting directly on the rat adrenal gland: the possible involvement of zona medullaris.
Neuropeptide K (NPK), a member of the kassinin-like tachykinin family, is contained in the rat hypothalamus and is known to stimulate pituitary ACTH release. The intraperitoneal bolus administration of NPK dose-dependently enhanced corticosterone blood level not only in intact rats, but also in hypophysectomized/ACTH replaced animals. NPK did not affect corticosterone secretion of dispersed rat adrenocortical cells; however, it concentration-dependently raised basal corticosterone production by decapsulated adrenal quarters (including both cortical and medullary tissues). Minimal and maximal effective concentrations were 10(-9) and 10(-8) M, respectively. 10(-8) M NPK potentiated corticosterone response of adrenal quarters elicited by 10(-12) M ACTH, but not that evoked by higher concentrations of ACTH. The direct corticosterone secretagogue effect of 10(-8) M NPK is annulled by 10(-6) M alpha-helical-CRH or corticotropin-inhibiting peptide, competitive inhibitors of CRH and ACTH, respectively. In light of these findings, the hypothesis is advanced that NPK exerts a direct stimulatory action on adrenocortical secretion and that the mechanism underlying this effect of NPK may involve the activation of the intra-medullary CRH/ACTH system.
Department of Anatomy, University of Padua, Italy.
G
G
Mazzocchi
L K
LK
Malendowicz
P G
PG
Andreis
V
V
Meneghelli
A
A
Markowska
A S
AS
Belloni
G G
GG
Nussdorfer
D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism*; D000313:Adrenal Medulla / Q000187:drug effects / Q000502:physiology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D003345:Corticosterone / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D007016:Hypophysectomy; D007274:Injections, Intraperitoneal; D008297:Male; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015320:Tachykinins
D009479:Neuropeptides; D015320:Tachykinins; C045206:neuropeptide K; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone