Lack of effect of vasoactive intestinal peptide antagonists on blood flow in the rat thyroid.
We used three putative vasoactive intestinal peptide (VIP) antagonists: 1) [4C1-D-Phe6,Leu17]VIP, 2) [N-Ac-Tyr1,D-Phe2] GRF(1-29)-NH2, and 3) VIP(10-28) to assess the involvement of endogenous VIP in the regulation of thyroid hormone secretion and thyroid blood flow (BF). We measured thyroid BF in ketamine-pentobarbital-anesthetized rats using the microsphere technique. Increases in thyroid BF induced by VIP administration (30 pmol-1.5 nmol/100 g b.wt.) were not affected by any of the three compounds tested at doses 10-100 times higher than that of VIP. These compounds (3-15 nmol/100 g b.wt.) also failed to affect basal thyroid BF or hormone secretion. Increases in pancreatic and salivary gland BFs induced by VIP (30 pmol/100 g b.wt.) were also not affected by [4C1-D-Phe6,Leu17]VIP or [N-Ac-Tyr1,D-Phe2]GRF(1-29)-NH2 (3 nmol/100 g b.wt.). These results indicate that the three compounds tested are not effective inhibitors of VIP receptors in the thyroid vasculature and, therefore, they cannot be used in the investigation of the functional significance of endogenous VIP in the regulation of thyroid BF.
Michalkiewicz
M
M
Department of Physiology, West Virginia University Health Sciences Center, Morgantown 26506.
Huffman
L J
LJ
Hedge
G A
GA
D000818:Animals; D013007:Growth Hormone-Releasing Hormone / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects; D017337:Sermorelin / Q000031:analogs & derivatives; D013961:Thyroid Gland / Q000098:blood supply / Q000187:drug effects*; D013963:Thyroid Hormones / Q000097:blood; D014660:Vasoactive Intestinal Peptide / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D010446:Peptide Fragments; D013963:Thyroid Hormones; C048507:vasoactive intestinal peptide, 4-chloro-Phe(6)-Leu(17)-; D014660:Vasoactive Intestinal Peptide; C047945:vasoactive intestinal peptide (10-28); D017337:Sermorelin; D013007:Growth Hormone-Releasing Hormone; C045616:somatotropin releasing hormone (1-29)-amide, N-Ac-Tyr(1)-Phe(2)-