title: Phorbol ester, not growth hormone releasing factor, consistently stimulates growth hormone release from somatotroph adenomas in culture.
abstract: In order to study the mechanism of GH secretion from somatotroph adenoma cells, we have compared the effect of 12-O-tetradecanoyl phorbol-13-acetate (TPA) with that of growth hormone releasing factor (GRF) on GH secretion from human somatotroph adenoma cells cultured in monolayer. Pituitary adenoma cells were obtained from 13 patients with acromegaly undergoing surgery. On the 7th day of culture, the cells were exposed for 2 h to secretagogues. All 13 adenoma cell cultures (100%) responded to TPA (1.6-16.0 nmol/l) with a two- to six-fold increase in GH release (240 +/- 37% increase of control: mean +/- SE). The response was detectable within 10 min, and was maximal at 2 h. Phospholipase C (7.7 mmol/l) also stimulated a two- to ten-fold increase in GH release in all four adenomas examined (100%). GH release was stimulated by GRF (2.0 nmol/l) in eight out of 12 adenoma cells (67%), but the magnitude of the responses to GRF (60 +/- 18% increase of control: mean +/- SE) were much smaller than that of TPA. Five out of 13 adenomas secreted detectable amount of PRL into the medium and these five adenomas (100%) responded to TPA (16.0 nmol/l) with a two- to six-fold increase. These observations indicate that the activation of protein kinase C is the consistent stimulator in GH and PRL secretion in human somatotroph adenoma cells. However, it is not determined whether the protein kinase C is involved in the in-vivo production of GH in patients with acromegaly.
authors.affiliation: Department of Medicine, Tokyo Women's Medical College, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Emoto
authors.forename: E
authors.initials: E
authors.lastname: Ohmura
authors.forename: O
authors.initials: O
authors.lastname: Isozaki
authors.forename: T
authors.initials: T
authors.lastname: Tsushima
authors.forename: K
authors.initials: K
authors.lastname: Shizume
authors.forename: H
authors.initials: H
authors.lastname: Demura
mesh_terms: D000236:Adenoma / Q000378:metabolism*; D000328:Adult; D000368:Aged; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000378:metabolism*; D013268:Stimulation, Chemical; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate