Calcium-activated chloride conductance of lactotrophs: Comparison of activation in normal and tumoral cells during thyrotropin-releasing-hormone stimulation
✍ Scribed by P. Sartor; L. Dufy-Barbe; P. Vacher; B. Dufy
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 981 KB
- Volume
- 126
- Category
- Article
- ISSN
- 0022-2631
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✦ Synopsis
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.