title: Selective effect of castration on the anterior pituitary VIP receptor of male rats.
abstract: We investigated the effect of surgical castration of male rats on the binding of [Tyr(125I)10]VIP to receptors on the anterior pituitary gland, superior mesenteric artery, brain, liver, and prostate gland. In anterior pituitary membranes the maximum number of VIP binding sites was increased whereas binding affinity was decreased 24 hours following castration. In particular, the high affinity equilibrium dissociation constant (KD) increased from 0.13 +/- 0.02 nM (mean +/- SEM) to 0.67 +/- 0.07 nM and the maximum number of high affinity binding sites (Bmax) increased from 71 +/- 9 to 470 +/- 112 fmol/mg protein. No significant change was observed in the other tissues. Anesthesia or sham operation did not alter the anterior pituitary VIP receptor binding parameters. The changes in the VIP receptor 24 hours after castration were prevented by prior injection of testosterone. These findings demonstrate tissue-selective alterations to the anterior pituitary VIP receptor by castration that are likely mediated by withdrawal of testosterone.
authors.affiliation: Department of Medicine, University of Calgary, Alberta, Canada.
authors.forename: I E
authors.initials: IE
authors.lastname: Wanke
authors.forename: M
authors.initials: M
authors.lastname: Huang
authors.forename: O P
authors.initials: OP
authors.lastname: Rorstad
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D001921:Brain / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008566:Membranes / Q000378:metabolism; D008638:Mesenteric Arteries / Q000378:metabolism; D009919:Orchiectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011467:Prostate / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D018005:Receptors, Vasoactive Intestinal Peptide; D013574:Synaptosomes / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
chemical_list: D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide