Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

Abstract

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 GI), and 50 pF, respectively. Under the voltage-clamp condition, no voltagedependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time-and voltage-independent K + current. The ACh-induced hyperpolarization and K + current persisted, while the His response desensitized quickly (< 1 rain). These effects of ACh and His were mediated predominantly by m3-muscarinic and Hi-His receptors, respectively. The K + current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca2+-activated K + channel current (IK.ca)-The measurement of intracellular Ca 2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca-When EGTA in the pipette solution was increased from 0.15 to 10 raM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate /K.Ca by increasing [Cae+]i in JR-1 ceils. In the Ca2+-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca 2+ (1.8 raM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca 2+ release-related initial transient activation and the Ca 2+ influx-related sustained activation of 1K.Ca. Probably because of desensitization, the Ca 2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without IP3 is essentially involved not only in agonist-induced Ca ~+ release from the intracellular store but also in agonist-mediated Ca 2+ influx across the cell membrane in JR-1 cells. However, upon reapplication of [Ca2÷]o after a brief exposure of cells to the Ca2+-free bathing solution (during which the Ca 2+ influx-related component of Iicc~ was abolished), intracellular IP3 (with and without IP4) did not cause immediate recovery of the Ca 2+ influx-related I~.c~, but restored it with a very slow time course (the haft-recovery time of ~ 2-5 rain). This slow recovery was markedly accelerated by the application of ACh. This result suggests that ACh may generate an unidentified signal other than IP3 and IP4 responsible for Ca 2+ influx in JR-1 ceils.

Mechanisms of secretion-associated shrinkage and volume recovery in cultured rabbit parietal cells

“…Intermediate-conductance K ϩ channels have been implicated in Ca 2ϩ -activated K ϩ -secretion in colonic crypt cells (10) as well as K ϩ currents in a gastric epithelial cell line (15). A 50 -100 nM concentration of charybdotoxin was reported to be effective for blocking these channels (10,15), and 100 nM caused a significant decrease of [ 14 C]aminopyrine uptake during carbachol, but not forskolin treatment (Fig.…”

Mechanisms of L‐NG nitroarginine/indomethacin‐resistant relaxation in bovine and porcine coronary arteries

“…The involvement of pertussis toxin-sensitive G protein in muscarinic receptor-mediated inhibition of Ca2'-activated K+ channels has been described in vascular smooth muscle cells (Kume & Kotlikoff, 1991), airway smooth muscle cells (Kume et al, 1995) and colonic smooth muscle (Cole et al, 1989). Furthermore G protein-regulated K+ channels have been shown in the epithelial-cell line (Hemada et al, 1993), cortical collecting duct cells (Suzuki et al, 1994), adrenal chromaffin cells (Cannon et al, 1994) and rabbit atrai (Ray & Macheod, 1994). Since the nature of L-NG nitroarginine-resistant muscle cell relaxation remains unclear, we cannot speculate whether this compound or pathway relaxes smooth muscle cells via a receptor-G protein-K+ channel cascade or via direct activation of G protein within the smooth muscle membrane.…”

Macrolide Antibiotics Inhibit Mucus Secretion and Calcium Entry in Swine Airway Submucosal Mucous Gland Cells

“…An increase in [Ca 2ϩ ] i is required for ion channel activities and mucin release stimulated by acetylcholine (ACh), histamine, and ATP (Hamada et al, 1993;Choi et al, 2005;Farley, 2005, 2007). In most nonexcitable cells such as SMGCs, membrane receptor activation induces Ca 2ϩ release from internal stores and Ca 2ϩ influx through store-operated Ca 2ϩ channels (SOCs) or receptor-operated channels (ROCs) (Takemura and Ohshika, 1991;Vig and Kinet, 2007).…”