Evidence for furosemide-sensitive Na+-K+-Cl- co-transport in lactating rat mammary tissue.
The transport of K+ (using 86Rb as tracer) by lactating rat mammary tissue slices has been studied in order to seek evidence for Na+-K+-Cl- co-transport. Potassium transport was inhibited by furosemide; the locus of inhibition was at a site other than the Na+:K+ pump. Replacing medium Cl- with NO3 reduced the bidirectional movement of K+; moreover, furosemide was without effect in a Cl- -free medium. Sodium replacement by N-methyl-D-glucamine acted to reduce the loop diuretic-sensitive component of K+ uptake whilst concomitantly increasing K+ influx via an ouabain- and furosemide-resistant pathway. Potassium efflux was found to be transiently stimulated by Na+ ions; this was attenuated by furosemide. Potassium egress was markedly increased via a furosemide-insensitive pathway when salicylate was used to replace Cl-. The results are consistent with furosemide-sensitive Na+-K+-Cl- co-transport.
Shennan
D B
DB
Hannah Research Institute, Scotland.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D005665:Furosemide / Q000494:pharmacology*; D007700:Kinetics; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008536:Meglumine / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D012459:Salicylates / Q000494:pharmacology; D020156:Salicylic Acid; D012964:Sodium / Q000378:metabolism*; D013861:Thiocyanates / Q000494:pharmacology
D002712:Chlorides; D009566:Nitrates; D012459:Salicylates; D013861:Thiocyanates; D010042:Ouabain; D008536:Meglumine; D005665:Furosemide; D012964:Sodium; D020156:Salicylic Acid; D011188:Potassium