title: Experimental determination of net protein charge, [A]tot, and Ka of nonvolatile buffers in bird plasma.
abstract: The quantitative mechanistic acid-base approach to clinical assessment of acid-base status requires species-specific values for [A]tot (the total concentration of nonvolatile buffers in plasma) and Ka (the effective dissociation constant for weak acids in plasma). The aim of this study was to determine [A]tot and Ka values for plasma in domestic pigeons. Plasma from 12 healthy commercial domestic pigeons was tonometered with 20% CO2 at 37 degrees C. Plasma pH, Pco2, and plasma concentrations of strong cations (Na, K, Ca), strong anions (Cl, L-lactate), and nonvolatile buffer ions (total protein, albumin, phosphate) were measured over a pH range of 6.8-7.7. Strong ion difference (SID) (SID5=Na+K+Ca-Cl-lactate) was used to calculate [A]tot and Ka from the measured pH and Pco2 and SID5. Mean (+/-SD) values for bird plasma were as follows: [A]tot=7.76+/-2.15 mmol/l (equivalent to 0.32 mmol/g of total protein, 0.51 mmol/g of albumin, 0.23 mmol/g of total solids); Ka=2.15+/-1.15x10(-7); and pKa=6.67. The net protein charge at normal pH (7.43) was estimated to be 6 meq/l; this value indicates that pigeon plasma has a much lower anion gap value than mammals after adjusting for high mean L-lactate concentrations induced by restraint during blood sampling. This finding indicates that plasma proteins in pigeons have a much lower net anion charge than mammalian plasma protein. An incidental finding was that total protein concentration measured by a multianalyzer system was consistently lower than the value for total solids measured by refractometer.
authors.affiliation: Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1. hstaempf@uoguelph.ca
authors.forename: Henry
authors.initials: H
authors.lastname: Stämpfli
authors.forename: Michael
authors.initials: M
authors.lastname: Taylor
authors.forename: Carl
authors.initials: C
authors.lastname: McNicoll
authors.forename: Ady Y
authors.initials: AY
authors.lastname: Gancz
authors.forename: Peter D
authors.initials: PD
authors.lastname: Constable
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000138:Acidosis / Q000503:physiopathology; D000818:Animals; D000838:Anions / Q000097:blood; D001639:Bicarbonates / Q000097:blood; D001774:Blood Chemical Analysis; D001798:Blood Proteins / Q000032:analysis / Q000737:chemistry*; D002021:Buffers; D002245:Carbon Dioxide / Q000097:blood; D002412:Cations / Q000097:blood; D010856:Columbidae / Q000097:blood*; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000097:blood / Q000502:physiology*; D012709:Serum Albumin / Q000502:physiology*; D013045:Species Specificity
chemical_list: D000838:Anions; D001639:Bicarbonates; D001798:Blood Proteins; D002021:Buffers; D002412:Cations; D010710:Phosphates; D012709:Serum Albumin; D002245:Carbon Dioxide