Regulation of L-type Calcium Channels in Pituitary GH4C1 Cells by Depolarization
| Autor: | Ravikumar Peri, David J. Triggle, Satpal Singh |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
medicine.medical_specialty
Calcium Channels L-Type Voltage-dependent calcium channel Voltage-gated ion channel Chemistry Paroxysmal depolarizing shift Calcium channel T-type calcium channel Cardiac action potential Depolarization Cell Biology Biochemistry Cell Line Membrane Potentials Rats Endocrinology Pituitary Gland Anterior Internal medicine medicine Biophysics Animals L-type calcium channel Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 276:31667-31673 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m102613200 |
| Popis: | The neurosecretory anterior pituitary GH(4)C(1) cells exhibit the high voltage-activated dihydropyridine-sensitive L-type and the low voltage-activated T-type calcium currents. The activity of L-type calcium channels is tightly coupled to secretion of prolactin and other hormones in these cells. Depolarization induced by elevated extracellular K(+) reduces the dihydropyridine (+)-[(3)H]PN200-110 binding site density and (45)Ca(2+) uptake in these cells (). This study presents a functional analysis by electrophysiological techniques of short term regulation of L-type Ca(2+) channels in GH(4)C(1) cells by membrane depolarization. Depolarization of GH(4)C(1) cells by 50 mm K(+) rapidly reduced the barium currents through L-type calcium channels by approximately 70% and shifted the voltage dependence of activation by 10 mV to more depolarized potentials. Down-regulation depended on the strength of the depolarizing stimuli and was reversible. The currents recovered to near control levels on repolarization. Down-regulation of the calcium channel currents was calcium-dependent but may not have been due to excessive accumulation of intracellular calcium. Membrane depolarization by voltage clamping and by veratridine also produced a down-regulation of calcium channel currents. The down-regulation of the currents had an autocrine component. This study reveals a calcium-dependent down-regulation of the L-type calcium channel currents by depolarization. |
| Databáze: | OpenAIRE |
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