Blockade by lithium ions of potassium channels in rat anterior pituitary cells
| Autor: | P. M. Lledo, M. Kato, J. D. Vincent |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Male
medicine.medical_specialty Potassium Channels Physiology Lithium Anterior pituitary Pituitary Gland Anterior Internal medicine medicine Extracellular Animals Gallopamil Patch clamp Ions Chemistry Depolarization Cell Biology Growth hormone secretion Potassium channel Rats Electrophysiology Endocrinology medicine.anatomical_structure Growth Hormone Biophysics Intracellular Endocrine gland |
| Zdroj: | American Journal of Physiology-Cell Physiology. 261:C218-C223 |
| ISSN: | 1522-1563 0363-6143 |
| Popis: | Extracellular Li+ has been known to facilitate the basal secretion of growth hormone from anterior pituitary cells and of catecholamine from chromaffin cells. In both cases, the intracellular accumulation of Li+ seems to be the prerequisite, and the presence of extracellular Ca2+ is indispensable. In this series of experiments, we examined whether Li+ blocked K+ currents by using primary cultured anterior pituitary cells from male rats. K+ currents were measured in the whole cell configuration of the patch-clamp technique. Extracellular Li+ (140 mM) suppressed both the delayed rectifier K+ current (IK) and the transient outward K+ current to 71 and 69% of control, respectively, in a reversible manner. IK elicited by a voltage step to +70 mV from holding potential of -70 mV was suppressed by 32.5 mM internal Li+ to 28% of control. Half-maximal suppression of K+ conductance by internal Li+ was 16 mM. Furthermore, Ca(2+)-channel blocker methoxyverapamil potently suppressed Li(+)-induced growth hormone secretion. From these results we propose that the blockade by Li+ of K+ channels could depolarize the cells and activate Ca2+ channels, thereby promoting the influx of Ca2+ and hormone secretion as a mechanism of Li(+)-induced hormone secretion. |
| Databáze: | OpenAIRE |
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