Distribution of H+ and HCO3 minus between CSF and blood during metabolic acidosis in dogs.
To determine whether the regulation of brain extracellular fluid acid-base balance is by active ion transport or passive distribution, changes in cisternal and lumbar cerebrospinal fluid (CSF) (H+) and (HCO3 minus) were assessed in five dogs with normal acid-base status and in six dogs during metabolic acidosis. Both groups were mechanically ventilated to maintain a constant PaCO2. The pH, PCO2, (HCO3 minus), and (lactate) in CSF and arterial plasma and the CSF/plasma DC potential difference were determined at intervals, and the electrochemical potential differnces (mu) for H+ and HCO3 minus were calculated. Following control measurements at pHa equal to 7.40, metabolic acidosis was induced by infusion of 0.6 N HCl. Measurements were made 0, 3, 4.5, and 6 h thereafter and at 0, 3, and 6 h in the control series. A steady state for ion distribution was reached by 4.5 h. In the control series at 6 h the values of mu for H+ and HCO3 minus were within minus 0.2 and +0.5 mV of initial values at the cistern and +0.1 and +0.9 mV at the lumbar site. During metabolic acidosis, the 6-h values at the cistern returned to 0.0 and +0.7 mV of control for muH+ and muHCO3 minus while lumbar values returned to +0.5 and minus 0.4 mV. The closeness of these 6-h values of mu to control is compatible with passive distribution of H+ and HCO3 minus between CSF and blood.
D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism*; D001692:Biological Transport; D001769:Blood; D002245:Carbon Dioxide / Q000097:blood / Q000134:cerebrospinal fluid; D002555:Cerebrospinal Fluid; D004285:Dogs; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood / Q000134:cerebrospinal fluid; D013997:Time Factors
D001639:Bicarbonates; D007773:Lactates; D002245:Carbon Dioxide