A MAXI CL- CHANNEL COUPLED TO ENDOTHELIN-B RECEPTORS IN THE BASOLATERAL MEMBRANE OF GUINEA-PIG PARIETAL-CELLS

作者：KAJITA H; KOTERA T; SHIRAKATA Y; UEDA S; OKUMA M; ODAOHMAE K; TAKIMOTO M; URADE Y; OKADA Y

来源：The Journal of Physiology, 1995, 488(1): 65-75.

1. To study endothelin (ET) receptors in guinea-pig stomach, ET-binding assays and in vitro autoradiography were performed on fundic cell suspensions and on sections of the fundus, respectively. ET(A) and ET(B) receptor subtypes were found to coexist in the parietal cells.
2. Endothelin 1 (ET-1) added to the (basolateral) bathing solution was found to activate noisy whole-cell Cl- currents within about 1 min in both single, isolated parietal cells and those within gastric glands obtained from the fundus.
3. ET-1-induced Cl- currents were rapidly blocked by a Cl- channel blocker (NPPB) added to the (basolateral) bathing solution in a concentration-dependent manner with a half-maximum inhibition concentration of 33 mu M.
4. The anion selectivity sequence of the ET-1-induced conductance was I->Br->Cl->F-, corresponding to Eisenman's sequence I.
5. Changes in extracellular pH between 5 and 8 did not affect the ET-1-induced activation of Cl- currents.
6. Similar activating effects were also observed with ET-3 and a specific ET(B) receptor agonist (IRL162O). An ET(B) receptor antagonist (IRL1720) prevented the ET-1 effect, whereas an ET(A)-selective antagonist (FR139317 or BQ123) failed to antagonize the ET-1 effect.
7. In the whole-cell mode, unitary Cl- channel events could be observed in association with ET-1-activated macroscopic currents. The single-channel conductances were around 200 and 350 pS at negative and positive membrane potentials, respectively.
8. It is concluded that gastric parietal cells of guinea-pig possess pH-insensitive 'maxi' Cl- channels coupled to ET(B) receptors in the basolateral membrane.

• 出版日期1995-10-1