Excess Heme in Sickle Erythrocyte Inside-Out Membranes: Possible Role in Thiol Oxidation

It has been suggested that the development of sickle RBC membrane defects might be related to abnormal amounts of membrane-associated heme (a term we use in its generic sense to include hemoglobins, hemichromes, and free heme). Techniques previously used to measure membrane heme, however, would not distinguish between what is truly membrane-associated and what is merely trapped in RBC ghost preparations. Consequently, we have examined extensively washed inside-out membranes (IOM) prepared from normal and sickle RBC. Approximately 25% of the sickle ghost heme is lost upon conversion to IOM, but sickle IOM still have a significant excess (1.6 ± 0.3 nmol heme /mg membrane protein compared with 0.7 ± 0.2 nmol/mg for normal IOM, P