Alteration in G proteins and prolactin levels in pituitary after ethanol and estrogen treatment.
BACKGROUND
Chronic administration of ethanol increases plasma prolactin levels and enhances estradiol's mitogenic action on the lactotropes of the pituitary gland. The present study was conducted to determine the changes in the pituitary levels of G proteins during the tumor development following alcohol and ethanol treatments.


METHODS
Using ovariectomized Fischer-344 female rats, we have determined ethanol and estradiol actions at 2 and 4 weeks on pituitary weight and pituitary cell contents of prolactin, Gs. Gq11, Gi1, Gi2, and Gi3 proteins. Western blots were employed to measure protein contents.


RESULTS
Ethanol increased basal and estradiol-enhanced wet weight and the prolactin content in the pituitary in a time-dependent manner. Chronic exposure of estradiol increased the levels of Gs protein in the pituitary. Unlike estradiol, ethanol exposure did not show significant effect on the basal level of Gs protein, but moderately increased the estradiol-induced levels of this protein. Estradiol exposure enhanced Gq11 protein levels in the pituitary after 2 and 4 weeks, while ethanol treatment failed to alter these protein levels in the pituitary in control-treated or estradiol-treated ovariectomized rats. In the case of Gi1, estradiol but not ethanol increased the level of this protein at 4 weeks of treatment. However, estradiol and ethanol alone reduced the levels of both Gi2 and Gi3 proteins at 2 and 4 weeks of treatment. Ethanol also significantly reduced the estradiol-induced Gi2 levels at 4 weeks and Gi3 level at 2 and 4 weeks.


CONCLUSIONS
These results confirm ethanol's and estradiol's growth-promoting and prolactin stimulating actions on lactotropes of the pituitary and further provide evidence that ethanol and estradiol may control lactotropic cell functions by altering expression of specific group of G proteins in the pituitary.
Chaturvedi
Kirti
K
Endocrine Program, Center of Alcohol Studies and Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA.
Sarkar
Dipak K
DK
D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344
D002492:Central Nervous System Depressants; D004967:Estrogens; D000431:Ethanol; D004958:Estradiol; D011388:Prolactin; D019204:GTP-Binding Proteins