PubMed · 6082727
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T E Williams, F J Lewis. 1967. Consistency check for acid-base data.. https://pubmed.ncbi.nlm.nih.gov/6082727/
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The vacuolar-type H+-ATPases (V-ATPases) are multimeric proton pumps involved in a wide variety of physiological processes. We have identified two alternative splicing variants of C2 subunit isoforms: C2-a, a lung-specific isoform containing a 46-amino acid insertion, and C2-b, a kidney-specific isoform without the insert. Immunohistochemistry with isoform-specific antibodies revealed that V-ATPase with C2-a is localized specifically in lamellar bodies of type II alveolar cells, whereas the C2-b isoform is found in the plasma membranes of renal alpha and beta intercalated cells. Immunoprecipitation combined with immunohistological analysis revealed that C2-b together with other kidney-specific isoforms was selectively assembled to form a unique proton pump in intercalated cells. Furthermore, a chimeric yeast V-ATPase with mouse the C2-a or C2-b isoform showed a lower Km(ATP) and lower proton transport activity than that with C1 or Vma5p (yeast C subunit). These results suggest that V-ATPases with the C2-a and C2-b isoform are involved in luminal acidification of lamellar bodies and regulation of the renal acid-base balance, respectively.
A general formalism for calculating parameters describing physiological acid-base balance in single compartments is extended to multicompartment systems and demonstrated for the multicompartment example of human whole blood. Expressions for total titratable base, strong ion difference, change in total titratable base, change in strong ion difference, and change in Van Slyke standard bicarbonate are derived, giving calculated values in agreement with experimental data. The equations for multicompartment systems are found to have the same mathematical interrelationships as those for single compartments, and the relationship of the present formalism to the traditional form of the Van Slyke equation is also demonstrated. The multicompartment model brings the strong ion difference theory to the same quantitative level as the base excess method.
The purpose of this study was to investigate cerebral energy metabolism and acid-base homeostasis during impaired oxygen supply in fetal sheep. Systemic acid-base balance was correlated with the sequence in changes of cerebral phosphorus metabolite ratios and intracellular pH. Phosphorus magnetic resonance spectra were obtained from the brain of six fetal sheep simultaneously with repeated measurements of fetal arterial oxygen saturation and acid-base balance. Fetal hypoxia was induced by gradually reducing the oxygen supply to the anesthetized pregnant ewe to establish an intended arterial pH of 7.00 or lower. The ratio of phosphocreatine to inorganic phosphate decreased from 1.08 +/- 0.10 (SD) during the control period to 0.77 +/- 0.29 at an arterial pH between 7.20 and 7.25. The inorganic phosphate level became significantly increased at an arterial pH between 7.10 and 7.15 compared with control values. With ongoing arterial acidosis, cerebral intracellular pH decreased linearly with the arterial pH. At an arterial pH of 7.00, cerebral intracellular pH was decreased from 7.18 +/- 0.03 to 6.71 +/- 0.28, and phosphocreatine and nucleoside triphosphates levels were decreased significantly. In fetal sheep brain, cerebral oxidative phosphorylation (ratio of phosphocreatine to inorganic phosphate) is already affected at a mild arterial acidosis. At an arterial pH of 7.00 or lower, nucleoside triphosphates disappeared, which almost inevitably was followed by death in fetal sheep.