Dopaminergic regulation of alpha-subunit secretion and messenger ribonucleic acid levels in alpha-secreting pituitary tumors.
Glycoprotein hormone and/or subunit secretion has been increasingly recognized in patients with pituitary nonsecretory adenomas and alpha-subunit secretion has been reported to occur in 5-10% of all pituitary tumors. We investigated the dopaminergic regulation of alpha-subunit secretion in four patients with alpha-subunit secreting pituitary adenomas documented by serum and immunocytochemical studies. In three of the four patients there was a significant decrease in serum alpha-subunit concentrations during 6 weeks of bromocriptine administration. Tumor size decreased in two patients. In pituitary tumor cells from one patient cultured in vitro, dopamine caused a highly significant decrease in media alpha-subunit concentrations. To investigate whether dopaminergic regulation of alpha-subunit secretion occurs at a pre- or posttranslational level, messenger RNA (mRNA) from cultured tumor cells from one patient was analyzed by Northern blot techniques. A decrease in alpha-subunit mRNA occurred in cells incubated with 10(-10), 10(-8), and 10(-6) M dopamine. We conclude that dopamine suppressed pituitary tumor alpha-subunit secretion and mRNA levels. Dopamine agonists may be of benefit in the therapy of patients with such tumors.
D000236:Adenoma / Q000188:drug therapy / Q000378:metabolism*; D000328:Adult; D000368:Aged; D001971:Bromocriptine / Q000627:therapeutic use; D004298:Dopamine / Q000502:physiology*; D005260:Female; D015292:Glycoprotein Hormones, alpha Subunit; D007987:Gonadotropin-Releasing Hormone; D006651:Histocytochemistry; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D010908:Pituitary Hormones, Anterior / Q000235:genetics / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone; D014407:Tumor Cells, Cultured
D015292:Glycoprotein Hormones, alpha Subunit; D010908:Pituitary Hormones, Anterior; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D007987:Gonadotropin-Releasing Hormone; D001971:Bromocriptine; D013973:Thyrotropin-Releasing Hormone; D004298:Dopamine