Calcium-activated chloride conductance of lactotrophs : comparison of activation in normal and tumoral cells during thyrotropin-releasing-hormone stimulation

• Published in: The Journal of membrane biology 1992-02, Vol.126 (1), p.39-49
• Main Authors: SARTOR, P, DUFY-BARBE, L, VACHER, P, DUFY, B
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological Transport - drug effects; Biological Transport - physiology; Calcimycin - pharmacology; Calcium - pharmacology; Cell Membrane Permeability - drug effects; Cell Membrane Permeability - physiology; Cell physiology; Cells, Cultured; Chlorides - pharmacokinetics; Female; Fundamental and applied biological sciences. Psychology; Immunohistochemistry; Membrane and intracellular transports; Membrane Potentials - drug effects; Membrane Potentials - physiology; Molecular and cellular biology; Pituitary Gland, Anterior - cytology; Pituitary Gland, Anterior - physiology; Pituitary Neoplasms - pathology; Pituitary Neoplasms - physiopathology; Potassium - pharmacokinetics; Rats; Spectrometry, Fluorescence; Thyrotropin-Releasing Hormone - pharmacology; Tumor Cells, Cultured - drug effects; Tumor Cells, Cultured - pathology
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/BF00233459

We studied a chloride (Cl-) conductance activated by calcium (Ca2+) in normal rat lactotrophs and compared its activation during TRH stimulation in normal rat lactotrophs and in GH3 tumoral lactosomatotrophs cells, using the whole-cell configuration of the patch-clamp technique. The Cl- specificity of the conductance was assessed by manipulation of internal and external Cl- concentrations. The reversal potentials were in agreement with those predicted by the Nernst equation. Ca2+ ionophore A23187 and membrane depolarizations activated the Cl- conductance. However, a feedback effect of Cl- gradient modifications on Ca2+ movements was also observed in normal lactotrophs. In the latter, TRH (100 nM) mobilization of intracellular Ca2+ activated this Cl- conductance together with the potassium (K+) conductance when both ions were present in the intracellular medium (IM) or alone when K+ was absent. Chloride conductance was not activated in the GH3 cells, where mobilization of intracellular Ca2+ by TRH (100 nM) activated only Ca2(+)-dependent K+ conductance. It seems likely that the activation of Cl- conductance in these two different cell types involves different mechanisms.