The stimulated C-kinase activity in estradiol-treated rat pituitaries is reduced by chronic treatment with the dopamine agonist CV 205-502.
To investigate whether the modulation of lactotrope cell multiplication and prolactin secretion in rat pituitary glands implicated the phosphoinositide C-kinase system, female Wistar rats were treated or not-with the dopamine agonist CV 205-502 or 8 days or with estradiol cervical implants for 8 for 15 days, alone or in combination with CV 205-502 for the last 8 days. CV 205-502 treatment induced a significant reduction in plasma PRL levels and in pituitary weights, whereas estradiol treatment induced a significant increase in both parameters. CV 205-502, in association with estradiol, counteracted estradiol stimulation of PRL levels and of pituitary weights. Total C-kinase activity in controls was 29.8 +/- 9.9 pmol 32phosphorus/min (N = 7, mean +/- SEM), mainly found in the soluble fraction (84%). When administered alone, CV 205-502 induced a significant reduction (-58%, p less than 0.02) in C-kinase activity in the particulate fraction with no modification in the soluble fraction. Both 8 and 15 days estradiol treatment induced a significant stimulation of total C-kinase activity, 74% and 155% respectively. When combined with estradiol, CV 205-502 significantly (p less than 0.02) counteracted the estradiol increase in total C-kinase activity, which was only 45% over control values. We conclude that treatment with a dopamine agonist and estradiol, which have antagonistic effects on the pituitary, exerts an opposite regulation of C-kinase activity. Whether this may be one of the mechanisms involved in their interaction on pituitary lactotropes remains to be determined.
Birman
P
P
INSERM U.223(1), Faculté de Médecine Pitié-Salpêtrière, Paris, France.
Touraine
P
P
Bai-Grenier
F
F
Dubray
C
C
Kaabache
T
T
Peillon
F
F
Joubert
D
D
D019870:1-Phosphatidylinositol 4-Kinase; D000634:Aminoquinolines / Q000494:pharmacology*; D000818:Animals; D015259:Dopamine Agents / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D009929:Organ Size / Q000187:drug effects; D010770:Phosphotransferases / Q000378:metabolism*; D010902:Pituitary Gland / Q000201:enzymology*; D011388:Prolactin / Q000097:blood; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000634:Aminoquinolines; D015259:Dopamine Agents; D004958:Estradiol; C046650:quinagolide; D011388:Prolactin; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase; D011493:Protein Kinase C