Expression of prostacyclin receptors in luteinizing hormone-releasing hormone immortalized neurons: role in the control of hormone secretion.
PGs of the E series are involved in the control of LHRH secretion. The present experiments were conducted to clarify whether PGI2 (prostacyclin) might be also involved in such a control, using multiple methodological approaches on immortalized LHRH-secreting neurons. A RT-PCR procedure to detect mouse PGI2 receptor (IP) messenger RNA was first applied, and the results obtained showed the presence of a specific transcript in two cell lines of immortalized LHRH neurons (GT1-1 and GN11 cell lines). Receptor binding assays on membrane preparations from GT1-1 cells showed the presence of a single specific and saturable class of binding sites (Kd = 4.6 nM; 10,000 sites/cell) for [3H]iloprost, a stable analog of PGI2. Competition experiments showed that the binding sites labeled by [3H]iloprost possess the pharmacological characteristics of IP receptors. In functional studies, PGI2 and its analogs, iloprost and cicaprost, were able to stimulate LHRH release from the GT1-1 cells with elevated potencies (EC50 = 0.6-4.3 nM); PGE1 was only slightly less active (EC50 = 28.5 nM), whereas PGE2, considered the major PG involved in LHRH secretion, was poorly effective (EC50 = 921 nM). The relative potencies (EC50) of these compounds in stimulating the intracellular accumulation of cAMP were in line with their LHRH-releasing activities. In conclusion, these results indicate that immortalized LHRH-secreting neurons express IP receptors through which PGI2 may exert relevant effects on LHRH release.
Pimpinelli
F
F
Department of Endocrinology, Institute of Pharmacological Sciences, University of Milan, Italy.
Rovati
G E
GE
Capra
V
V
Piva
F
F
Martini
L
L
Maggi
R
R
D000818:Animals; D002461:Cell Line, Transformed / Q000187:drug effects / Q000378:metabolism; D002462:Cell Membrane; D000242:Cyclic AMP / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D011464:Epoprostenol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D016285:Iloprost / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin / Q000096:biosynthesis* / Q000235:genetics
D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin; D007987:Gonadotropin-Releasing Hormone; D011464:Epoprostenol; D000242:Cyclic AMP; D016285:Iloprost; D015232:Dinoprostone; C043867:cicaprost