G protein-coupled corticotropin-releasing hormone receptors in rat retina.
The presence of corticotropin-releasing hormone (CRH) receptors in rat retinal membranes was investigated by using [125I-Tyro]-ovine CRH ([125I]oCRH) as radioligand. The receptor binding was rapid, reversible, saturable and specific. The [125I]oCRH binding was completely displaced by different CRH-related peptides with a rank order of potency similar to that displayed in stimulating rat retinal adenylyl cyclase activity. Two populations of binding sites were detected: one with high affinity (Kd = 1.7 nM) and the other with low-affinity (Kd = 130 nM). The GTP analogue guanosine 5'-O-(3'-thiotriphosphate) reduced the high-affinity binding and increased the relative proportion of sites with low-affinity. Incubation of rat retinal membranes with the RM/1 antibody, which recognizes the carboxyl-terminus of the alpha subunit of the G protein Gs, prevented the CRH stimulation of adenylyl cyclase. In immunoblots, the RM/1 antibody recognized an immunoreactive protein band of 45 kDa and a protein with a similar electrophoretic mobility was ADP-ribosylated by cholera toxin. These data provide evidence for the presence of specific CRH receptors in rat retina and contribute to define the CRH signalling system in this tissue.
Olianas
M C
MC
Department of Neurosciences, University of Cagliari, Italy.
Onali
P
P
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D029845:Amphibian Proteins; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002772:Cholera Toxin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007700:Kinetics; D008297:Male; D036361:Peptide Hormones; D010455:Peptides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D014579:Urotensins / Q000378:metabolism
D029845:Amphibian Proteins; D036361:Peptide Hormones; D010455:Peptides; D018019:Receptors, Corticotropin-Releasing Hormone; D014579:Urotensins; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C025727:sauvagine; D002772:Cholera Toxin; D003346:Corticotropin-Releasing Hormone; C029676:urotensin I; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases