Acute orexin effects on insulin secretion in the rat: in vivo and in vitro studies.
Orexin-A and orexin-B are members of a family of newly described orexigenic hypothalamic neuropeptides. Scanty data are available suggesting the involvement of orexins in regulation of the secretion of pituitary hormones and in control of energy homeostasis. Present studies aimed to explain whether orexins affect blood insulin concentration and insulin secretion in the rat. To check this possibility, adult female rats were subcutaneously injected with different doses (1 or 2 nmol) of orexin-A or orexin-B. A bolus administration of orexin-A resulted in an increase in blood insulin (up to min 120) and glucose (60 min after injection) concentration. The higher dose of orexin-B, on the other hand, exerted effect on insulin secretion only at min 60 of experiment and neither doses changed blood glucose level. Only orexin-A stimulated insulin secretion in an in vitro perfusion system of the rat pancreas preparation, while orexin-B was less effective. The results demonstrate that orexins belong to a group of neuropeptides influencing insulin secretion and acting directly on the pancreas. Direct, at least partial, effect of orexin on insulin secretion may be connected with the regulation of metabolism by this peptide.
Nowak
K W
KW
Department of Animal Physiology and Biochemistry, August Cieszkowski University of Agriculture, Poznań, Poland. kwnowak@owl.au.poznan.pl
Maćkowiak
P
P
Switońska
M M
MM
Fabiś
M
M
Malendowicz
L K
LK
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002352:Carrier Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood* / Q000378:metabolism*; D000078790:Insulin Secretion; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D000068797:Orexins; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D001786:Blood Glucose; D002352:Carrier Proteins; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins