title: Characterization of two pituitary GH3 cell sublines partially resistant to apoptosis induction by okadaic acid.
abstract: Pituitary GH3 cells die by apoptosis when treated with okadaic acid, a specific inhibitor of ser/thr phosphatases. Incubations starting at concentrations of 5 and 12.5 nM followed by stepwise rises resulted in two populations (the S1 and S2 sublines) that proliferated at initially lethal 30 nM. Cells were partially resistant to higher concentrations of okadaic acid and its derivative methyl okadaate. Toxicity of the structurally distinct inhibitors cantharidic acid and calyculin A was differently affected in the two resistant lines. The enhanced expression of the P-glycoprotein was one mechanism of resistance in S1 and S2. Resistance was reversed completely (S1) or partially (S2) by the addition of verapamil. In addition, phosphatase activity, presumably PP2A, was increased in S2. Therefore, pharmacokinetic and pharmacodynamic mechanisms can protect pituitary GH3 cells from apoptotic cell death by okadaic acid.
authors.affiliation: Institute of Pharmacology & Toxicology, University of Göttingen, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Ritz
authors.forename: J
authors.initials: J
authors.lastname: Marwitz
authors.forename: E
authors.initials: E
authors.lastname: Richter
authors.forename: C
authors.initials: C
authors.lastname: Ziemann
authors.forename: I
authors.initials: I
authors.lastname: Quentin
authors.forename: H J
authors.initials: HJ
authors.lastname: Steinfelder
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053938:DNA Fragmentation; D018432:Drug Resistance, Multiple; D019319:Okadaic Acid / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000473:pathology*; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D019319:Okadaic Acid