title: Ventilation and CSF ions during isocapnic HCl and HNO3 acidosis in conscious rabbits.
abstract: In conscious rabbits with preimplanted arterial, central venous, and cisterna magna catheters, we infused HCl or HNO3 over 9 h to reduce plasma [HCO-3] by 9-14 mmol/l. We hypothesized that greater entry into cerebrospinal fluid (CSF) of a strong anion, NO-3 vs. Cl-, would reduce the strong ion difference and the [HCO-3], and we used isocapnic conditions to minimize the effects of PCO2-specific mechanisms of CSF HCO-3 regulation. Although CSF pH decreased slightly in both groups reflecting a small increase in CSF PCO2, we observed no significant change in CSF [HCO-3]. With HCl, there was no significant increase in CSF [Cl-], even though plasma [Cl-] increased 15-16 mmol/l. With HNO3, CSF [NO-3] increased 3.6-7.9 mmol/l, owing to the 18-22 mmol/l increase in plasma [NO-3], and resulted, not in a decrease in [HCO-3], as hypothesized, but in a decrease in [Cl-]. There was no difference in the ventilatory responses of the two groups. These results emphasize the importance of PCO2-dependent mechanisms in determining the CSF [HCO-3] and indicate that the strong anion mechanisms of CSF HCO-3 regulation can utilize changes in both NO-3 and Cl-.
mesh_terms: D000138:Acidosis / Q000097:blood / Q000134:cerebrospinal fluid* / Q000139:chemically induced / Q000503:physiopathology; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood*; D003243:Consciousness; D006851:Hydrochloric Acid; D007477:Ions; D009566:Nitrates; D017942:Nitric Acid; D011817:Rabbits; D012119:Respiration
chemical_list: D007477:Ions; D009566:Nitrates; D002245:Carbon Dioxide; D017942:Nitric Acid; D006851:Hydrochloric Acid