title: CSF HCO3- regulation in isosmotic conditions: the role of brain PCO2 and plasma HCO3-.
abstract: We have studied in anesthetized cats the response of CSF HCO3- to (1) an increase in CSF PCO2, plasma HCO3- controlled at the normal value; (2) an increase in plasma HCO3-, CSF PCO2 controlled at the normal value; and (3) an increase in both CSF PCO2 and plasma HCO3-. Plasma HCO3- was controlled via HCO3-/Cl- exchange without altering plasma Na concentration or osmolarity using the technique of peritoneal dialysis. The results suggest that CSF HCO3- regulation in these conditions is dependent on (1) a PCO2-dependent process in which HCO3- ions are formed in brain cells or choroid plexus and (2) an ionic movement of HCO3- from plasma to CSF dependent on an increase in plasma HCO3-. The first process is largely completed by 3 hours; the second takes 6 hours or more. An analysis of plasma and CSF HCO3-, Cl- and unmeasured anions (UA), (Na+ + K+ -CL- -HCO3-), suggests that CSF HCO3- regulation may be complex involving ionic exchanges of three or more anions between brain extracellular fluid, plasma and brain cells.
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001639:Bicarbonates / Q000097:blood / Q000134:cerebrospinal fluid* / Q000378:metabolism; D001921:Brain / Q000378:metabolism* / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D002415:Cats; D005260:Female; D008297:Male; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D002245:Carbon Dioxide; D012964:Sodium; D011188:Potassium