Peptide contents of neuropeptide Y, vasoactive intestinal polypeptide, and beta-calcitonin gene-related peptide and their messenger ribonucleic acids after dexamethasone treatment in the isolated rat islets of Langerhans.
A number of neuropeptides including neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), and beta-calcitonin gene related peptide (beta-CGRP) are known to influence insulin secretion. In order to investigate whether they might have a local autocrine/paracrine effect within the islets of Langerhans we screened isolated islets by Northern blot analysis and RIA for a number of peptides and found evidence for the presence of messenger RNA (mRNA) encoding NPY, VIP, and beta-CGRP. Dexamethasone treatment for 12 days increased the content of NPY, VIP, and beta-CGRP significantly from 1.3 +/- 0.3 to 19.8 +/- 1.6; 0.25 +/- 0.03 to 0.91 +/- 0.1; 2.2 +/- 0.2 to 4.8 +/- 0.1 fmol/islet respectively, mean +/- SEM (n = 4, P less than 0.05) and remained elevated 24 h after recovery. However when the results were normalized and expressed as a ratio of insulin content only NPY and VIP were significantly raised. Five days post treatment VIP was still significantly elevated compared to controls. mRNA for NPY increased 10-fold and for VIP increased 2 1/2 times after dexamethasone whereas mRNA for beta-CGRP was not significantly different from controls. Neither capsaicin nor 6-hydroxydopamine affected islet content or message of NPY, VIP, and beta-CGRP. Immunoreactive NPY and its mRNA were detected in two cultured beta-cell lines, HIT T-15 and RIN m5F cells whereas VIP and beta-CGRP were undetectable. The local islet synthesis of neuropeptides, which are known to influence islet hormone release pharmacologically, suggests the possibility that they may play a role in intraislet paracrine regulation.
Jamal
H
H
Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
Jones
P M
PM
Byrne
J
J
Suda
K
K
Ghatei
M A
MA
Kanse
S M
SM
Bloom
S R
SR
D000818:Animals; D015152:Blotting, Northern; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D014660:Vasoactive Intestinal Peptide / Q000235:genetics / Q000378:metabolism*
D009478:Neuropeptide Y; D012333:RNA, Messenger; D014660:Vasoactive Intestinal Peptide; D003907:Dexamethasone; D015740:Calcitonin Gene-Related Peptide