Dopamine inhibits the arachidonate and prolactin release stimulated by thyrotropin-releasing hormone through an islet-activating protein-sensitive GTP-binding protein in anterior pituitary cells.
Coupling of the dopamine (DA) receptor to the pathway of arachidonate (AA) through the islet-activating protein (IAP)-sensitive GTP-binding (G) protein was examined in primary cultures of anterior pituitary cells. The inhibitions by 1 microM DA of the stimulations of prolactin (PRL) release by 100 nM thyrotropin-releasing hormone and by 10 microM calcium ionophore A23187 were blocked by 100 ng/ml IAP. DA at 1 microM did not inhibit the release of [3H]-AA induced by 100 mU/ml phospholipase A2 (PLA2), but it inhibited the release of PRL induced by 100 mU/ml PLA2. This inhibition was blocked by 100 ng/ml IAP. IAP also blocked the inhibitions by DA of the releases of PRL by 5 microM AA and by 5 microM 5-hydroxyeicosatetraenoic acid. These results suggest that the DA receptor on lactotrophs is coupled to the pathway following the release of AA (lipoxygenase) through the IAP-sensitive G protein.
Ohmichi
M
M
Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
Hirota
K
K
Koike
K
K
Kadowaki
K
K
Yamaguchi
M
M
Miyake
A
A
Tanizawa
O
O
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D000001:Calcimycin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D004298:Dopamine / Q000502:physiology*; D005260:Female; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D006893:Hydroxyeicosatetraenoic Acids / Q000037:antagonists & inhibitors; D037342:Pertussis Toxin; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000037:antagonists & inhibitors; D014316:Tritium; D010566:Virulence Factors, Bordetella / Q000502:physiology*
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D011954:Receptors, Dopamine; D010566:Virulence Factors, Bordetella; D014316:Tritium; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016718:Arachidonic Acid; D000001:Calcimycin; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D037342:Pertussis Toxin; D010741:Phospholipases A; D054467:Phospholipases A2; D019204:GTP-Binding Proteins; D004298:Dopamine