Characterization of a growth hormone-releasing hormone binding site in the rat renal medulla.
Receptor binding analysis was performed in the renal medulla from 2-month-old rats, an extrapituitary tissue containing the highest level of GHRH receptor mRNA. At 4 degrees C, in the presence of a cocktail of protease inhibitors, binding of [125I-Tyr(10)]hGHRH (1-44)NH(2) to medullary homogenates was specific, time-dependent, reversible and saturable (K(d): 28 nM; B(max): 30 fmol/mgprot.). In these experimental conditions, no change of binding parameters could be detected in the course of aging. The structure-affinity profile was different in the two tissues and chemical cross-linking revealed the presence of 65-, 55- and 38-kDa 125I-GHRH-labeled complexes in the renal medulla compared to 65-, 47- and 28-kDa radioactive complexes in the anterior pituitary. It is suggested that GHRH binding sites, and possibly the receptor, may be different in the two tissues.
Boulanger
Luce
L
Laboratory of Neuroendocrinology of Aging, Department of Medicine, CHUM Research Center, Notre-Dame Hospital, University of Montreal, 1560 East Sherbrooke Street, Que., H2L 4M1, Montreal, Canada.
Girard
Nathalie
N
Strecko
Julie
J
Gaudreau
Pierrette
P
D000818:Animals; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D013007:Growth Hormone-Releasing Hormone / Q000737:chemistry*; D007679:Kidney Medulla / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature
D003432:Cross-Linking Reagents; D012333:RNA, Messenger; D013007:Growth Hormone-Releasing Hormone