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The binding of carbon dioxide by horse haemoglobin.

ABSTRACT: 1. Three modified horse haemoglobins have been prepared: (i) alpha(c) (2)beta(c) (2), in which both the alpha-amino groups of the alpha- and beta-chains have reacted with cyanate, (ii) alpha(c) (2)beta(2), in which the alpha-amino groups of the alpha-chains have reacted with cyanate, and (iii) alpha(2)beta(c) (2), in which the two alpha-amino groups of the beta-chain have reacted with cyanate. 2. The values of n (the Hill constant) for alpha(c) (2)beta(c) (2), alpha(2)beta(c) (2) and alpha(c) (2)beta(2) were (respectively) 2.5, 2.0 and 2.6, indicating the presence of co-operative interactions between the haem groups for all derivatives. 3. In the alkaline pH range (about pH8.0) all the derivatives show the same charge as normal haemoglobin whereas in the acid pH range (about pH6.0) alpha(c) (2)beta(c) (2) differs by four protonic charges and alpha(c) (2)beta(2), alpha(2)beta(c) (2) by two protonic charges from normal haemoglobin, indicating that the expected number of ionizing groups have been removed. 4. alpha(c) (2)beta(2) and alpha(c) (2)beta(c) (2) show a 25% decrease in the alkaline Bohr effect, in contrast with alpha(2)beta(c) (2), which has the same Bohr effect as normal haemoglobin. 5. The deoxy form of alpha(c) (2)beta(c) (2) does not bind more CO(2) than the oxy form of alpha(c) (2)beta(c) (2), whereas alpha(c) (2)beta(2) and alpha(2)beta(c) (2) show intermediate binding. 6. The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO(2) through the four terminal alpha-amino groups and that the two terminal alpha-amino groups of alpha-chains are involved in the Bohr effect.

SUBMITTER: Kilmartin JV

PROVIDER: S-EPMC1177110 | biostudies-other | 1971 Aug

REPOSITORIES: biostudies-other

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Project description:Mechanical ventilation (MV) represents a lifesaving treatment for patients with respiratory failure, but it could be harmful through the development of ventilator-induced lung injury (VILI). In patients with acute respiratory distress syndrome (ARDS), protective MV strategies with low tidal volume to minimize VILI have been demonstrated to reduce lung injury and mortality. However, they can be limited by the emergence of uncontrolled hypercapnia. Similarly, in COPD patients, noninvasive MV failure often is associated with a progressive rise in arterial CO2 and need for endotracheal intubation, with higher risk of hospital mortality. Minimally invasive extracorporeal CO2 removal systems (ECCO2R) theoretically can remove the entire amount of the CO2 produced in the body per minute. In ARDS patients, ECCO2R may further reduce the risk of VILI ensuring ultraprotective MV and avoiding hypercapnia. In patients with exacerbation of COPD, ECCO2R may help to avoid intubation or facilitate weaning from invasive MV. In intensive care unit, concomitant renal and respiratory failure with MV is one of the strongest risk factors for hospital mortality. Combining ECCO2R and renal replacement therapy may support respiratory and renal functions and limit the side effects of MV. However, the need for systemic anticoagulation and the related risk of bleeding still represent a concern for a wider application of ECCO2R devices. In conclusion, ECCO2R is an effective support therapy to MV to limit its invasiveness and side effects, but its efficacy and safety must be proven in well-designed clinical trials. Objectives This chapter will:1 Explain the physiology of CO2 removal during extracorporeal support.2 Describe potential clinical applications of extracorporeal CO2 removal systems (ECCO2R) support therapy in patients with acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) as well as in those with acute kidney injury requiring renal replacement therapy.

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The binding of carbon dioxide by horse haemoglobin.

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