title: Volume-activated K(+)(Rb(+)) efflux in lactating rat mammary tissue.
abstract: The effect of cell swelling, induced by a hyposmotic shock, on K(+)(Rb(+)) efflux from lactating rat mammary tissue explants has been studied. A hyposmotic challenge increased the fractional release of K(+)(Rb(+)) from mammary tissue in the absence and presence of the loop-diuretic bumetanide (100 microM). However, the volume-sensitive moiety of K(+)(Rb(+)) efflux was proportionately larger when bumetanide was present in the incubation medium. On the other hand, a hyposmotic shock appeared to reduce the bumetanide-sensitive component of K(+)(Rb(+)) efflux. The increase in K(+)(Rb(+)) efflux, induced by cell swelling, was dependent upon the extent of the hyposmotic challenge. In the presence of bumetanide, substituting Cl(-) with NO(3)(-) reduced the initial increase in volume-sensitive K(+)(Rb(+)) efflux. However, volume-sensitive K(+)(Rb(+)) release was prolonged in the presence of NO(3)(-). Volume-activated K(+)(Rb(+)) efflux from rat mammary tissue explants was inhibited by quinine. Cell swelling increased the intracellular concentration of Ca(2+) in a fashion which depended on the presence of extracellular Ca(2+). However, removing extracellular Ca(2+) did not inhibit volume-activated K(+)(Rb(+)) efflux from rat mammary tissue explants. The results are consistent with the presence of volume-activated K(+) channels in lactating rat mammary tissue. Volume-activated K(+) efflux may play a central role in mammary cell volume regulation.
authors: Hannah Reseach Institute, KA6 5HL, Ayr, UK. shennand@hri.sari.ac.uk
authors: D B
authors: DB
authors: Shennan
authors: I F
authors: IF
authors: Gow
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007774:Lactation; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012414:Rubidium Radioisotopes; D027981:Symporters; D014316:Tritium; D000096922:K Cl- Cotransporters
chemical_list: D002118:Calcium; D002352:Carrier Proteins; D002712:Chlorides; D011188:Potassium; D015221:Potassium Channels; D011803:Quinine; D012414:Rubidium Radioisotopes; D027981:Symporters; D014316:Tritium; D000096922:K Cl- Cotransporters