Chloride flux from blood to CSF: inhibition by furosemide and bumetanide.
Movement of chloride from blood to cerebrospinal fluid (CSF) is one of the factors that may be involved in regulation of CSF [Cl-], which is important to CSF acid-base balance. We made quantitative measurements of the unidirectional flux of radiolabeled chloride between blood and CSF in anesthetized dogs, using 38Cl, a short-lived isotope (half-life 37.3 min). This allowed multiple studies to be performed in a given animal. A three-compartment model for the blood, CSF, brain extracellular fluid, and ventriculocisternal perfusion system was used to determine the flux rate. With normocapnia, the flux was 0.01.1 min-1. The influx could be reproducibly measured for three separate determinations in the same animal over a period of 6 h, being 98 +/- 6% of the control first run on the second run and 113 +/- 6% on the third. Furosemide and bumetanide, inhibitors of sodium-coupled chloride movement, lowered the flux to 43 +/- 3% and 55 +/- 6% of control, respectively. The combination of hypercapnia and furosemide lowered the influx to 63 +/- 9% of control. These results indicate that a major mechanism of chloride entry into CSF is sodium-coupled chloride transport.
Johnson
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Pulmonary Unit, Massachusetts General Hospital, Boston.
Singer
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Hoop
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Kazemi
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D000818:Animals; D002034:Bumetanide / Q000494:pharmacology*; D002712:Chlorides / Q000097:blood / Q000134:cerebrospinal fluid*; D002713:Chlorine; D004232:Diuretics / Q000494:pharmacology*; D004285:Dogs; D005665:Furosemide / Q000494:pharmacology*; D006935:Hypercapnia / Q000378:metabolism; D008954:Models, Biological; D010477:Perfusion; D011868:Radioisotopes
D002712:Chlorides; D004232:Diuretics; D011868:Radioisotopes; D002034:Bumetanide; D002713:Chlorine; D005665:Furosemide