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In vivo regulation of plasma [H+] in ponies during acute changes in PCO2. J Appl Physiol (1985) 1990 Jan;68(1):316-21

Date

01/01/1990

Pubmed ID

2107166

DOI

10.1152/jappl.1990.68.1.316

Scopus ID

2-s2.0-0025089842   2 Citations

Abstract

The major objective of this study was to test the hypothesis that in ponies the change in plasma [H+] resulting from a change in PCO2 (delta H+/delta PCO2) is less under acute in vivo conditions than under in vitro conditions. Elevation of inspired CO2 and lowering of inspired O2 (causing hyperventilation) were used to respectively increase and decrease arterial PCO2 (Paco2) by 5-8 Torr from normal. Arterial and mixed venous blood were simultaneously sampled in 12 ponies during eucapnia and 5-60 min after Paco2 had changed. In vitro data were obtained by equilibrating blood in a tonometer at five different levels of PCO2. The in vitro slopes of the H+ vs. PCO2 relationships were 0.73 +/- 0.01 and 0.69 +/- 0.01 neq.1-1.Torr-1 for oxygenated and partially deoxygenated blood, respectively. These slopes were greater (P less than 0.001) than the in vivo H+ vs. PCO2 slopes of 0.61 +/- 0.03 and 0.57 +/- 0.03 for arterial and mixed venous blood, respectively. The delta HCO3-/delta pH (Slykes) was 15.4 +/- 1.1 and 17.0 +/- 1.1 for in vitro oxygenated and partially deoxygenated blood, respectively. These values were lower (P less than 0.001) than the in vivo values of 23.3 +/- 2.7 and 25.2 +/- 4.7 Slykes for arterial and mixed venous blood, respectively. In vitro, plasma strong ion difference (SID) increased 4.5 +/- 0.2 meq/l (P less than 0.001) when Pco2 was increased from 25 to 55 Torr. A 3.5-meq/l decrease in [Cl-] (P less than 0.001) and a 1.3 +/- 0.1 meq/l increase in [Na+] (P less than 0.001) accounted for the SID change.(ABSTRACT TRUNCATED AT 250 WORDS)

Author List

Forster HV, Murphy CL, Brice AG, Pan LG, Lowry TF

Author

Hubert V. Forster PhD Professor in the Physiology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Acid-Base Equilibrium
Acidosis, Respiratory
Alkalosis, Respiratory
Animals
Carbon Dioxide
Horses
Hydrogen-Ion Concentration
Hyperventilation
jenkins-FCD Prod-403 0f9a74600e4e79798f8fa6f545ea115f3dd948b2