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.
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.
Luce
L
Boulanger
Nathalie
N
Girard
Julie
J
Strecko
Pierrette
P
Gaudreau
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