Characterization of VIP-and helodermin-preferring receptors on rat platelets.
We have examined the binding of radio-iodinated vasoactive intestinal peptide (VIP) to rat platelets. The binding was time- and temperature-dependent and was reversible, saturable and specific. Scatchard analysis of binding data suggested the presence of a single class of binding sites, with Kd = 2.49 +/- 0.76 nM and Bmax = 112.1 +/- 54.6 fmol/10(8) cells. Several VIP-related peptides inhibited 125I-VIP binding to rat platelets with the following order of potency: helodermin > or = VIP > peptide histidine isoleucine. Glucagon, secretin, growth hormone-releasing hormone (GHRH), and gastric inhibitory peptide (GIP) were ineffective. VIP and the other peptides increased cyclic AMP production with the same order of potency as the inhibition of binding, but the stimulation by VIP was less marked than that by prostacyclin (PGI2). We conclude that rat platelets have functional, adenylate cyclase-linked, receptors that bind preferentially to helodermin and VIP.
Shima
K
K
First Department of Internal Medicine, Nagoya University School of Medicine, Aichi, Japan.
Sakakibara
H
H
Said
S I
SI
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001792:Blood Platelets / Q000737:chemistry* / Q000378:metabolism; D002452:Cell Count; D000242:Cyclic AMP / Q000378:metabolism; D011464:Epoprostenol / Q000494:pharmacology; D005749:Gastric Inhibitory Polypeptide / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D010455:Peptides / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018005:Receptors, Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012633:Secretin / Q000494:pharmacology; D013696:Temperature; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D018005:Receptors, Vasoactive Intestinal Peptide; D012633:Secretin; D014660:Vasoactive Intestinal Peptide; D005749:Gastric Inhibitory Polypeptide; C040442:heliodermin; D005934:Glucagon; D013007:Growth Hormone-Releasing Hormone; D011464:Epoprostenol; D000242:Cyclic AMP