Neuropeptide Y enhances LHRH binding to rat gonadotrophs in primary culture.
Incubation of dispersed adenohypophyseal cells from intact male rats with Neuropeptide Y (NPY) or Peptide YY (YY) at 21 degrees C increased maximal 125I LHRHa binding (Bmax) by about 50%. In presence of 10(-7) M NPY, Bmax calculated from saturation isotherm curves was 15.3 +/- 1.9 fmoles x mg-1 proteins, as compared to 10 +/- 1 fmoles x mg-1 in control incubates. The increase was dose dependent with an EC50 of 6.3 +/- 1.8 10(-10) M NPY. Preincubation of the cells with pertussis toxin (PT, 15 ng/ml) for 24 h abolished the effect, suggesting coupling of NPY receptors to G alpha o or G alpha i proteins. NPY 10(-7) M inhibited basal and Forskolin 10(-5) M stimulated intracellular cyclic AMP formation by 31.9 +/- 3.4% and 30.6 +/- 2.3% respectively. Desensitization of protein kinase C by overnight preincubation of the cells with 10(-6) M phorbol ester (PMA) did not interfere with the effect of NPY. In contrast, W7, a calmodulin inhibitor, as well as H7, a protein kinase C inhibitor with a relatively wide spectrum, suppressed the effect of NPY with IC50 of 1.4 +/- 0.6 10(-6) M and 2.2 +/- 0.5 10(-5) M, respectively. Taken together, these results suggest that NPY is able to control unmasking of a cryptic LHRH receptor pool in pituitary cells by a process dependent upon both GTP binding proteins and calmodulin dependent protein kinase.
Leblanc
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P
Unité de Dynamique des Systèmes Neuroendocriniens INSERM U 159, Paris, France.
L'Héritier
A
A
Rasolonjanahary
R
R
Kordon
C
C
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology*; D037342:Pertussis Toxin; D010879:Piperazines / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002147:Calmodulin; D007546:Isoquinolines; D009478:Neuropeptide Y; D010879:Piperazines; D013449:Sulfonamides; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D007987:Gonadotropin-Releasing Hormone; C017967:W 7; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate