Localization and regulation of a functional GHRH receptor in the rat renal medulla.
To provide information about the kidney GHRH receptor (GHRH-R), we assessed its tissue and cellular localization, defined its pattern of expression in developing and aging rats, and studied the effects of GHRH on the regulation of GHRH-R mRNA levels and receptor internalization. In situ hybridization and ribonuclease protection assay demonstrated that GHRH-R mRNA is restricted to the Henle's loop (HL). GHRH-R mRNA levels were low in the medulla from 3- and 12-d-old male rats, increased significantly in that from 30- to 70-d-old rats, and decreased in that from 12- and 18-month-old animals. Compared with the GHRH-R mRNA profile obtained in the pituitary, these data support the concept of a tissue-specific regulation of GHRH-R. In HL cell cultures from 70-d-old rats, a 4-h incubation with 1-100 nM rat GHRH-(1-29)NH(2) reduced GHRH-R mRNA levels significantly. As anti-GHRH-R- (392-404) immunoreactivity was demonstrated in HL cells, internalization of [N(alpha)-5-carboxyfluoresceinyl-D-Ala(2),Ala(8), Ala(15),Lys(22)]hGHRH-(1-29)NH(2) in a time- and temperature-dependent manner and inhibition of this process by phenyl arsine oxide indicate that desensitization to GHRH involves both GHRH-R internalization and down-regulation of GHRH-R mRNA levels. Localization of a functional GHRH-R in HL and its regulation during development and aging suggest roles associated with cellular proliferation, differentiation, and/or water/electrolyte transport.
Boisvert
Chantale
C
Laboratory of Neuroendocrinology of Aging, Centre Hospitalier de l'Université Montréal Research Center, Notre Dame Hospital and Department of Medicine, University of Montréal, Montréal, Québec, Canada H2L 4M1.
Paré
Caroline
C
Veyrat-Durebex
Christelle
C
Robert
Alma
A
Dubuisson
Sophie
S
Morel
Gérard
G
Gaudreau
Pierrette
P
D000818:Animals; D015152:Blotting, Northern; D002469:Cell Separation; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D008138:Loop of Henle / Q000166:cytology / Q000378:metabolism; D008297:Male; D023282:Nuclease Protection Assays; D010903:Pituitary Gland, Anterior / Q000254:growth & development / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011966:Receptors, LHRH / Q000096:biosynthesis* / Q000235:genetics
D012333:RNA, Messenger; D011966:Receptors, LHRH