Potassium transport in isolated cerebral microvessels from the rat.
Microvessels have been prepared from the gray matter of a rat brain by a technique involving density gradient centrifugation. A suspension of these vessels, largely capillaries, was incubated in vitro in order to investigate K transport. The flux of K (as 86Rb) into and out of endothelial cells was estimated. Potassium influx was sensitive to temperature and pH of the medium, and was markedly inhibited by 1 mM ouabain (45%). Ouabain did not inhibit K efflux, as anticipated, when Na-K pumps are mainly located on the abluminal plasma membrane of the endothelial cell. The ouabain-sensitive K influx was measured at varying external concentrations of K. The Km of ouabain-sensitive K influx was 2.95 mM, which is similar to the affinity of the transport carrier of K, found in in vivo studies of K efflux from brain to the blood system. Both 1 mM furosemide and 5 mM barium chloride inhibited part of the ouabain-insensitive K influx. Potassium efflux was not influenced by furosemide, but was somewhat reduced by barium chloride. Noradrenalin (10(-3) mM) and histamine (0.1 mM) did not significantly affect the influx of K.
D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D002196:Capillaries / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002560:Cerebrovascular Circulation / Q000187:drug effects; D002712:Chlorides; D004727:Endothelium / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008433:Mathematics; D008833:Microcirculation; D008855:Microscopy, Electron, Scanning; D008858:Microscopy, Phase-Contrast; D009638:Norepinephrine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism
D017609:Barium Compounds; D002712:Chlorides; C024986:barium chloride; D001464:Barium; D010042:Ouabain; D005665:Furosemide; D006632:Histamine; D012413:Rubidium; D011188:Potassium; D009638:Norepinephrine