PubMed · 47400
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R J Barr, M Bonin. 1975-03-03. Letter: Polyvinyl chloride.. https://doi.org/10.1001/jama.231.9.914b
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The regulation of Cl- channels in human myoballs by G proteins was studied using whole-cell and inside-out patch recordings. After perfusion of the cell with 0.1 mM GTP[gamma S], the specific Cl- conductance, GCl, at standard resting potential (-85 mV) was increased from 5.9 microS/cm2 to 103 microS/cm2, and the kinetics upon stepping the potential to positive values was changed from an activating current with very slow inactivation to a fast inactivating current with no potential-dependent activation. These effects were not affected by the simultaneous blockade of several signal cascades involving G proteins. Addition of the protein kinase blockers PKI (25 microM), H8 (10 microM), or of the phospholipase-A2-blocking agent quinacrine (10 microM), had not much influence on these GTP[gamma S] effects. Buffering of the intracellular Ca2+ concentration (0.1 microM) or addition of the Ca2+/calmodulin antagonist trifluoperazine (50 microM) was also without effect. Pre-incubation of the cells with pertussis toxin or with cholera toxin did not change GCl. In excised inside-out patches voltage-clamped at -85 mV, application of GTP[gamma S] influenced the "intermediate" Cl- channel, the Cl- channel type having the highest density in these cells, by increasing the number of transitions in a half-conductance state. The probability of the channel being in one of the two conducting states rose from 0.015 to 0.67, and the kinetics of the single-channel currents was changed so that, on average, it was similar to the whole-cell current kinetics seen after application of GTP[gamma S]. It is concluded that a G protein is directly interacting with these channels.
Cystic fibrosis (CF) is the most frequent inheritable disease with a lethal course. One of the major problems of the disease is malabsorption and malnutrition, due to pancreatic insufficiency which is already present at birth in more than 85% of the patients. Characteristically the mucoid secretion products of the epithelial tissues in lung, pancreas, liver and intestine have a high viscosity. The pathophysiology is characterized by obstruction of these organs with secondary damage and finally destruction. For a long period intestinal obstruction syndromes in CF were ascribed only to the pancreatic insufficiency. Malabsorption is not only caused by enzyme deficiency but is also related to transport processes to the surface of the enterocytes. This indicates that the intestinal disorders in CF are partly the result of mucoid plugging and not only of pancreatic insufficiency. Recently in vitro studies have shown a blockade of secretion through chloride channels in the mucosal membrane of CF tissues. In vivo measurements of chloride fluxes in the rectum showed a disturbed regulation in CF patients. The high viscosity of the mucus and plugging is directly related to the diminished chloride secretion. So it is postulated that the abnormal chloride secretion is responsible for the intestinal obstruction and partially also for the malabsorption.
Explore the source record for details and available documents.