title: Handling of tracer bicarbonate by the liver. The relative impermeability of hepatocyte cell membranes to the ionic species.
abstract: The multiple indicator dilution technique was used to study transfer of labeled HCO3- across the hepatocyte membrane in the anesthetized mongrel dog. A bolus of H[14C]O3-, 51Cr-labeled erythrocytes, [36Cl-] and/or [3H]sucrose, and [3H]OH was injected through a catheter in the portal vein, and timed anaerobic blood samples were obtained from a catheter in the hepatic vein. Experiments were carried out in untreated controls and after intravenous infusion of acetazolamide (100 mg/kg). In the controls, the H[14C]O3- curve was very similar to the [3H]OH curve. The dilution curves were all linear transformations of each other, indicating that HCO3-, as had previously been shown for the other diffusible tracers, undergoes delayed-wave flow-limited distribution. The distribution space for H[14C]O3- in the control situation includes the blood plasma and interstitial spaces, the erythrocyte interior modified by a Donnan equilibrium, and the available liver cellular space. The calculated HCO3- concentration in the liver cells was somewhat lower than that in the plasma space; the difference implied a cellular pH lower than that of plasma by approximately 0.08 pH units. When the carbonic anhydrases were inhibited with acetazolamide, the dilution curve for H[14C]O3- changed radically, approaching that for [36Cl-], which does not enter the liver cells. The change indicates that although HCO3-, like Cl-, is rapidly exchanged between plasma and erythrocytes, it also does not readily penetrate hepatocytes unless previously transformed to carbon dioxide by the carbonic anhydrases.
authors.affiliation: McGill University Medical Clinic, Montreal General Hospital, Quebec, Canada.
authors.forename: A J
authors.initials: AJ
authors.lastname: Schwab
authors.forename: C A
authors.initials: CA
authors.lastname: Goresky
authors.forename: C P
authors.initials: CP
authors.lastname: Rose
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D002245:Carbon Dioxide / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000378:metabolism; D002463:Cell Membrane Permeability; D004285:Dogs; D004912:Erythrocytes / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000378:metabolism*; D012995:Solubility
chemical_list: D001639:Bicarbonates; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases; D000086:Acetazolamide