"In situ" characterization of GnRH receptors: use of two radioimagers and comparison with quantitative autoradiography.
New radioimagers, the HRRI (high resolution radioimager) and the Phosphorimager (phosphor screen : PS), apt to display more ample linear dose-response scale than radio-sensitive films, were tested in comparison with quantitative autoradiography (QA). GnRH receptor saturation experiments were achieved on tissue sections (rat pituitary, rat brain, human ovary) with a iodinate GnRH agonist (125I-[D-Ala6,Des-Gly10]-LH-RH Ethylamide) for determination of affinity constant (Kd). In rat pituitary, comparable results were obtained with the 3 methods (Kd: 0.4 to 0.6 nM). Discrepancies occurred in the hippocampus and in the granulosa cell layer of the preovulatory follicle, due to low resolutive (PS) or short linear dose-response (films) performances. In the hippocampus GnRH receptor affinity was under-estimated with PS (Kd: 2.3 vs 0.5 and 0.6 nM for QA and HRRI respectively). In the follicular granulosa cell layer it was over-estimated by QA (0.5 vs 50 nM for the HRRI), while PS did not allow resolution of this thin cell layer. In conclusion, the HRRI is a very powerful tool for the quantification of in situ radioligand binding (binding sites study and in situ hybridization) in very discrete areas.
Crumeyrolle-Arias
M
M
Pharmacologie N.I.E., Institut Pasteur, Paris, France.
Latouche
J
J
Laniece
P
P
Charon
Y
Y
Tricoire
H
H
Valentin
L
L
Roux
P
P
Mirambeau
G
G
Leblanc
P
P
Fillion
G
G
D000328:Adult; D000818:Animals; D001345:Autoradiography; D001923:Brain Chemistry; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D008297:Male; D010053:Ovary / Q000737:chemistry; D010902:Pituitary Gland / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D011966:Receptors, LHRH / Q000032:analysis* / Q000378:metabolism
C082465:LHRH ethylamide, des-Gly(10)-Ala(6)-; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone