Sub-pS Cl^– channels (0.3-0.4 pS) are present in the basolateral membrane of rabbit and rat parietal cells and have unique physiological roles. This Cl^– channel has a housekeeping role through dominating the cell membrane potential (Sakai et al. 1992), and the channel is activated via a prostaglandin E₂/nitric oxide/cyclic GMP-dependent pathway (Sakai et al. 1995). The channel activity is inhibited by pertussis toxin-insensitive G-protein-mediated production of superoxide anion (O₂^–) (Sakai & Takeguchi, 1994). Recently, we found that interleukin-1β (IL-1β) inhibited the channel activity (Sakai et al. 2001).

Herein, we investigated whether IL-1β induces the intracellular production of oxygen radicals using the isolated rabbit gastric glands loaded with the oxidant-sensing fluorescent probe, dihydrofluorescein diacetate. We also studied the signalling mechanism of the IL-1β-induced production of O₂^–. Rabbits were killed by intraperitoneal administration of an overdose of urethane (> 2 g kg^-1). Preparation of gastric glands and whole-cell patch-clamp experiments were performed as previously described (Sakai & Takeguchi, 1994). Data are shown as means ± S.E.M. Fluorescence intensity is expressed in arbitrary units. Differences between groups were analysed by one-way ANOVA. Comparison between the two groups was made by Student’s t test.

In the whole-cell recordings, the intracellular addition of superoxide dismutase (100 units ml^-1), a scavenger of O₂^–, and GDPβS (500 µM) abolished the IL-1β (1 ng ml^-1)-induced inhibition of the Cl^– current. Northern blot analysis showed that G_α13 mRNA (5.8 and 7.9 kb) was highly expressed in rabbit gastric parietal cells. G_α12 mRNA (3.7 kb) was also expressed in the parietal cells. Y-27632 (10 µM), a specific inhibitor of Rho-kinase, abolished the IL-1β-induced effect. In dihydrofluorescein diacetate-loaded single parietal cells, IL-1β (1 ng ml^-1) increased the production of oxygen radicals. Recombinant IL-1 receptor antagonist (500 ng ml^-1) significantly inhibited the IL-1β-stimulated production of oxygen radicals (51.5 ± 5.5-9.3 ± 5.6 (arbitrary units), P < 0.01, n = 4). Y-27632 (10 µM) also inhibited the effect of IL-1β (53.0 ± 11.6-8.0 ± 3.1 (arbitrary units), P < 0.05, n = 4). We suggest that IL-1β inhibits the sub-pS Cl^– channels of rabbit gastric parietal cells by G₁₂/G₁₃-mediated Rho/Rho-kinase-dependent production of O₂^–.