| Autor: |
S D, Cannon, S P, Wilson, K B, Walsh |
| Rok vydání: |
1994 |
| Předmět: |
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| Zdroj: |
Molecular pharmacology. 45(1) |
| ISSN: |
0026-895X |
| Popis: |
Guanine nucleotide binding proteins (G proteins) act as signal transducers between membrane receptors and ion channels. In the present study, the whole-cell arrangement of the patch clamp technique was used to examine the effect of G proteins on K+ channels in cultured bovine adrenal chromaffin cells. Internal dialysis of chromaffin cells with guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) or external application of AIF-4, to stimulate G proteins, resulted in a voltage-dependent increase in the amplitude of the outward K+ currents. The half-maximal voltage required for activation of the currents was shifted by -16 mV in the presence of GTP gamma S. The augmentation in the K+ currents was accompanied by the appearance of a fast component of current activation measured at potentials positive to 0 mV. The GTP gamma S-sensitive current could not be detected when internal K+ was replaced with Cs+ and was reversibly inhibited by tetraethylammonium (IC50, 2 mM). In contrast, the scorpion venom charybdotoxin (50 nM) and the bee venom apamin (250 nM) only slightly reduced the K+ currents during stimulation by GTP gamma S and did not alter the activation kinetics. In addition, the GTP gamma S-sensitive K+ current could be activated in the absence of internal Ca2+ and when the inward Ca2+ current was inhibited with CdCl2. Treatment of the chromaffin cells with fluoride decreased nicotine-evoked secretion of catecholamines in a concentration-dependent manner. Thus, bovine chromaffin cells contain a G protein-stimulated K+ channel that may play a regulatory role in secretagogue-mediated exocytosis. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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