| Autor: |
Harley, J. D., Robin, Helen |
| Zdroj: |
Australian Journal of Experimental Biology & Medical Science; Aug1963, Vol. 41 Issue 4, p281-292, 12p |
| Abstrakt: |
The conversion of oxyhaemoglobin (HbO2) to methaemoglobin (MetHb) in normal adult erythrocytes is potently catalysed by some naphthoquinones. Under appropriate conditions, the following mechanisms appear to regulate the degree of MetHb formation: (1) catalysis of NADPH-dependent reduction of MetHb by naphthoquinones; (2) the normal process of NADH-dependent reduction of MetHb, plus an increase in rate under certain circumstances due to catalysis by naphthoquinones; (3) the phenomena whereby the rates of NADH- and NADPH-dependent reduction of MetHb increase with increasing concentrations of MetHb; (4) retardation of MetHb formation as a result of catalase activity. Despite these regulating mechanisms, similar relative degrees of MetHb formation and CSH depletion were found in normal erythrocytes exposed to naphthoquinones In the presence of glucose. Oxidative destruction of haemoglobin and osmotic hyperfragility occurred only after gross depletion of CSH. Short of concentrations of 1,2-naphthoquinone which caused irreversible damage to adult erythrocytes, the pentose phosphate pathway appeared to compensate for metabolic variations which predispose to MetHb formation In erythrocytes taken from the umbilical cord. It Is suggested that the pentose phosphate pathway not only facilitates erythrocytic adaptation by responding to oxidant stress, but also maintains balance between the degrees of methaemoglobinaemia and haemolysis in erythrocytes exposed to naphthoquinones. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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