Chloride and Potassium Conductances of Mouse Pancreatic Zymogen Granules Are Inversely Regulated by a ≈80-kDa mdr1a Gene Product

Abstract

Cl؊ and cation conductances were characterized in zymogen granules (ZG) isolated from the pancreas of wild-type mice (؉/؉) or mice with a homozygous disruption of the multidrug resistance P-glycoprotein gene mdr1a (؊/؊). Cl ؊ conductance of ZG was assayed in isotonic KCl buffer by measuring osmotic lysis, which was induced by maximal permeabilization of ZG membranes (ZGM) for K ؉ with valinomycin due to influx of K

Calcium-dependent enzyme activation and vacuole formation in the apical granular region of pancreatic acinar cells

“…CCK hyperstimulation liberates Ca 2ϩ from granules in intact acinar cells (34), and this could increase [Ca 2ϩ ] i close to the cytosolic face of the granule membrane, potentially opening Ca 2ϩ -activated K ϩ channels (29). There is a K ϩ conductance pathway in the ZG membrane (35) that is regulated by a high-affinity dihydropyridine-binding protein (36). X-ray microanalysis of both frozen hydrated and dehydrated sections of pancreas shows that a relatively high concentration of CCK (1 nM) evokes a marked reduction in the Ca 2ϩ concentration and a marked increase in the K ϩ concentration inside the ZGs (34).…”

Regulation of the water channel aquaporin‐1: isolation and reconstitution of the regulatory complex

“…Studies using isolated ZGs from the exocrine pancreas and parotid glands demonstrate the presence of Cl and ATP-sensitive K + selective ion channels at the vesicle membrane, whose activities have been implicated in vesicle swelling (Fuller et al, 1989a,b;Gasser et al, 1988;Gasser and Hopfer, 1990;Segawa et al, 1991;Takuma et al, 1993;Thevenod et al, 1990Thevenod et al, , 1992Thevenod et al, , 1996. Furthermore, secretion of ZG contents in permeabilized pancreatic acinar cells requires the presence of both K + and Cl ions (Curran and Brodwick, 1991).…”

Up-regulation of Multidrug Resistance P-glycoprotein via Nuclear Factor-κB Activation Protects Kidney Proximal Tubule Cells from Cadmium- and Reactive Oxygen Species-induced Apoptosis

“…Following centrifugation at 12,000 ϫ g for 5 min, proteins (50 g/lane) were separated by SDS-polyacrylamide gel electrophoresis on 7.5% acrylamide Laemmli minigels, transferred onto polyvinylidene difluoride membranes, and the membranes blocked essentially as described earlier (12,17,22). Blots were incubated at 4°C with primary antibodies against mdr1 (0.5 g/ml), IB-␣ (0.05 g/ml), or NF-B p65/RelA (0.2 g/ml) overnight, incubated with horseradish peroxidase-conjugated secondary antibodies (1:10,000 dilution) for 60 min at 4°C, developed, visualized on x-ray films, and processed for documentation and quantitative analysis as described elsewhere (12,17,22,23).…”