定常空気呼吸時の血漿炭酸イオン濃度とCO_2分圧の関係
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概要
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The bicarbonate concentration in vivo, [HCO_3^-], has a Pco_2-dependent component, [HCO_3^-]^*, and a metabolic component, [HCO_3^－]^o. The [HCO_3^-]^* in elderly patients and volunteers was expressed by an exponential function of Pco_2 obtained by analysis of the venous-arterial (a-v) difference in [HCO_3^－]. The slope of [HCO_3^－]^* against Pco_2 was about 25% higher than that measured in oxygenated and deoxygenated blood in vitro. The regression functions of constituent ions were all linear versus [HCO_3^－]^* and [HCO_3^－]^o over the physiological Pco_2 range. The relationship between Pco_2 and [HCO_3^－]^* agreed well with that calculated from the CO_2 reaction rates on the active site of carbonic anhydrase using the Michaelis-Menten equation. At steady state the a-v difference in [HCO_3^－] is proportional to that in O_2 content ([O_2]) as estimated from the respiratory quotient (RQ). Thus, [HCO_3^－]^* inevitably implied the Haldane effect component of [HCO_3^－] ([HCO_3^－]_HE). However, [HCO_3^－] measured in oxygenated and deoxygenated blood was free from the change in [O_2] or the Haldane effect. The relationship between [HCO_3^－]_HE and [HCO_3^－]^* could be evaluated from the in vivo and in vitro difference in [HCO_3^－], and the effect of RQ on [HCO_3^-]_HE For analysing the ionic concentrations in plasma at steady state and the acid-base status, the equation for [HCO_3^－]^* was considered indispensable. Key words : Haldane effect of [HCO_3^－], CO_2 reaction rates, Carbonic anhydrase, Respiratory quotient, Strong ion difference
- 山形大学の論文
- 2004-02-16
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