Pertussis toxin inhibits somatostatin-induced K+ conductance in human pituitary tumor cells.
The effect of pertussis toxin on somatostatin-induced K+ current was examined in dissociated human pituitary tumor cells obtained from two acromegalic patients. Somatostatin-induced hyperpolarization or K+ current was observed in 20 of 23 cells in adenoma 1 and 10 of 11 cells in adenoma 2. After treatment with pertussis toxin for 24 h, these responses were completely suppressed (0/14 in adenoma 1, 0/10 in adenoma 2). Spontaneous action potentials, K+, Na+, and Ca2+ currents were well preserved after pertussis toxin treatment. When crude membrane fraction was incubated with [32P]NAD, a 41K protein was ADP-ribosylated by pertussis toxin. Hormone release was inhibited by somatostatin and this inhibition was blocked by pertussis toxin treatment.
D000200:Action Potentials / Q000187:drug effects; D000236:Adenoma / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D037342:Pertussis Toxin; D010911:Pituitary Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D011188:Potassium / Q000502:physiology*; D013004:Somatostatin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D007473:Ion Channels; D010566:Virulence Factors, Bordetella; D013004:Somatostatin; D037342:Pertussis Toxin; D011188:Potassium