title: 4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid inhibits adrenocorticotropin secretion from anterior pituitary cells.
abstract: Mouse clonal ACTH-secreting corticotrophs (AtT-20 cells) possess a membrane Ca2+-activated Cl- conductance which is partially blocked by the disulfonic stilbene derivative 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). In the current study the effect of SITS on the ACTH secretory process was evaluated. SITS markedly blocked basal and forskolin-stimulated ACTH secretion from AtT-20 cells (IC50 = 2.7 x 10(-4) M). Both CRF-induced ACTH secretion and forskolin-stimulated GH secretion from acutely dispersed rat anterior pituitary cells were inhibited by SITS (IC50 = 2.4 and 1.3 x 10(-4) M, respectively). SITS did not alter unstimulated or forskolin-elicited cAMP synthesis in AtT-20 cells, and in fact, could inhibit ACTH secretion in response to cAMP-independent agonists such as the calcium channel activator BAY-K-8644 or the protein kinase-C activator 12-tetradecanoyl-phorbol-13-acetate (IC50 = 2.6 and 2.4 x 10(-4) M, respectively). SITS did not alter the secretion of amylase from isolated exocrine pancreatic acinar cells. Its action was also fully reversible; after its removal from the incubation medium, cells secreted ACTH without a change in response to forskolin activation. Increasing extracellular Ca2+ or the addition of up to 10(-3) M tetraethylammonium or 4-aminopyridine did not reverse the inhibitory pattern of SITS action, suggesting that its inhibitory effect is most likely not due to hyperpolarization of AtT-20 cell membranes. The inability of amiloride to inhibit ACTH secretion further suggests that inhibition of ACTH secretion provoked by SITS is not due to a blockade of Cl-/HCO3- exchange. On the other hand, SITS was able to block 44% of basal 36Cl uptake by AtT-20 cells. Exchange of incubation medium chloride for gluconate or a reduction in the osmotic strength of the medium reduced both basal and secretagogue-stimulated ACTH secretion. The data suggest that SITS may modulate chloride-dependent, osmotically driven secretion from AtT-20 cells.
authors: Unité de Biorégulation Cellulaire, Centre Hospitalier de l'Université Laval, Sainte-Foy, Quebec, Canada.
authors: S
authors: S
authors: Heisler
authors: L
authors: L
authors: Jeandel
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013267:Stilbenes / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D013267:Stilbenes; D005576:Colforsin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000001:Calcimycin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium