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High affinity peptide histidine isoleucine-preferring receptors in rat liver

Journal Article · · Life Sci.; (United States)
Peptide Histidine Isoleucine (PHI) is generally considered a low affinity agonist for Vasoactive Intestinal Peptide (VIP) receptors. In this study, the authors investigated the presence of characteristics of (/sup 125/I)-PHI binding sites on rat liver membranes. Detergents at nonsolubilizing concentrations were included in the assay buffer to reduce adsorptive loss of PHI to acceptable levels and permit measurement of PHI-binding to receptors. Under these conditions, binding of PHI to liver membranes was time- and temperature-dependent, reversible and saturable. Unlabeled PHI was 9.7-fold more potent than VIP, and 357-fold more potent than secretin in displacing (/sup 125/I)-PHI binding. Scatchard analysis suggested the presence of two classes of PHI receptors, with Kd 27 pM and 512 pM. The data from (/sup 125/I)-PHI and (/sup 125/I)-VIP binding studies suggested that one class of receptors was PHI-preferring, and the other, equally reactive with PHI and VIP. The concentration of immunoreactive PHI, measured by radioimmunoassay, in blood from the hepatic portal vein of anesthetized rats was 2-fold higher than that from the hepatic vein, suggesting uptake of circulating PHI by the liver. 25 references, 3 figures, 1 table.
Research Organization:
Oklahoma Univ. Health Sciences Center, Oklahoma City
OSTI ID:
5520856
Journal Information:
Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 41:21; ISSN LIFSA
Country of Publication:
United States
Language:
English