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Distribution of the Vasotocin Subtype Four Receptor ( VT 4 R ) in the Anterior Pituitary Gland of the Chicken, G allus gallus , and its Possible Role in the Avian Stress Response
Author(s) -
Selvam R.,
Jurkevich A.,
Kang S. W.,
Mikhailova M. V.,
Cornett L. E.,
Kuenzel W. J.
Publication year - 2013
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2012.02370.x
Subject(s) - vasotocin , medicine , endocrinology , anterior pituitary , pars intermedia , vasopressin , biology , corticotropic cell , pituitary gland , receptor , polyclonal antibodies , neuropeptide , antibody , hormone , immunology
The neurohormone arginine vasotocin ( AVT ) in non mammalian vertebrates is homologous to arginine vasopressin ( AVP ) in mammals. Its actions are mediated via G protein‐coupled receptors that belong to the vasotocin/mesotocin family. Because of the known regulatory effects of nonapeptide hormones on anterior pituitary functions, receptor subtypes in that family have been proposed to be located in anterior pituitary cells. Recently, an avian vasotocin receptor subtype designated VT 4 R has been cloned, which shares 69% sequence homology with a human vasopressin receptor, the V 1a R . In the present study, a polyclonal antibody to the VT 4 R was developed and validated to confirm its specificity to the VT 4 R . The antibody was used to test the hypothesis that the VT 4 R is present in the avian anterior pituitary and is specifically associated with certain cell types, where its expression is modulated by acute stress. Western blotting of membrane protein extracts from pituitary tissue, the use of H e L a cells transfected with the VT 4 R and peptide competition assays all confirmed the specificity of the antibody to the VT 4 R . Dual‐labelling immunofluorescence microscopy was utilised to identify pituitary cell types that contained immunoreactive VT 4 R . The receptor was found to be widely distributed throughout the cephalic lobe but not in the caudal lobe of the anterior pituitary. Immunoreactive VT 4 R was associated with corticotrophs. Approximately 89% of immunolabelled corticotrophs were shown to contain the VT 4 R . The immunoreactive VT 4 R was not found in gonadotrophs, somatotrophs or lactotrophs. To determine a possible functional role of the VT 4 R and previously characterised VT 2 R , gene expression levels in the anterior pituitary were determined after acute immobilisation stress by quantitative reverse transcriptase‐polymerase chain reaction. The results showed a significant increase in plasma corticosterone levels (three‐ to four‐fold), a significant reduction of VT 4 R m RNA and an increase of VT 2 R m RNA (P < 0.05) in acutely immobilised chicks compared to controls. The data suggest a role of the VT 4 R in the avian stress response.