| Autor: |
Fatherazi, Sahba, Cook, Daniel |
| Zdroj: |
Journal of Membrane Biology; 1991, Vol. 120 Issue 2, p105-114, 10p |
| Abstrakt: |
The effects of tetraethylammonium (TEA) and quinine on Ca-activated [K(Ca)]. ATP-sensitive [K(ATP)]K channels and delayed-rectifier K current [K(dr)] have been studied in cultured insulin-secreting HIT cells using the patch-clamp technique. K(Ca) and K(ATP) channels were identified in excised, outside/ out patches using physiological solutions and had unitary conductances of 60.8±1.3 pS ( n=31) and 15.4±0.3 pS ( n=40). respectively. Macroscopic K(dr) current (peak current=607±100 pA at +50 mV, n=14) were recorded in the presence of 100 μ m cadmium and 0.5 μ m tetrodotoxin. Tetraethylammonium (TEA) blocked all three channel types but was more effective on K(Ca) channels (EC=0.15 mm) than on K(ATP) channels (EC=15 mm) or K(dr) currents (EC=3 mm). Quinine also blocked all three currents but was less effective on K(Ca) channels (EC=0.3 mm) while equally effective against K(ATP) channels and K(dr) currents (EC=0.025 mm). TEA blocked K(Ca) and K(ATP)_channels by reducing their single-channel conductances and decreasing the probability of K(ATP) channel opening. Quinine blocked K(Ca) channels by reducing the single-channel conductance, but blocked K(ATP) channels by reducing the probability of channel opening. Reinterpretation of previous microelectrode studies in light of these findings suggest that, ( i) only K(ATP) channels are active in low glucose, ( ii) both K(Ca) and K(dr) channels may assist Ca-spike repolarization, and ( iii) K(Ca) channels play no role in forming the burst pattern of Ca spiking in the B cell. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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