Effects of Ca2+ and furosemide on Cl- transport and O2 uptake in rat parotid acini.
Stimulation-induced changes in Cl- content and O2 consumption of collagenase-isolated rat parotid acini were measured. In less than 10 s, carbachol caused a net Cl- efflux, corresponding to approximately 50% of the Cl- content, and increased the O2 uptake by 100%. The increase was inhibitable by ouabain and was dependent on the presence of extracellular Ca2+. Furosemide reduced the unstimulated 36Cl- uptake and prevented the reuptake of Cl- after carbachol-induced release. This suggests that a cotransport system is operating in both the unstimulated and stimulated states. Furthermore, furosemide inhibited the stimulated ouabain-sensitive O2 uptake. Raising intracellular Ca2+ by the calcium ionophore A23187 evoked the same pattern of Cl- loss and O2 uptake as carbachol. Our results are compatible with the following hypothesis. Carbachol raises intracellular Ca2+, causing an increased Cl- permeability of the luminal membrane, resulting in a net Cl- efflux. A subsequently enhanced influx of Cl- and Na+ via a furosemide-sensitive cotransport system increases intracellular Na+. This stimulates the Na+-K+-ATPase and thereby the O2 consumption.
D000818:Animals; D001693:Biological Transport, Active; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology* / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002712:Chlorides; D007473:Ion Channels; D000001:Calcimycin; D010042:Ouabain; D005665:Furosemide; D002217:Carbachol; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium