Lead ions but not other metallic ions increase resistance to hypotonic lysis in prenatal hemopoiesis red blood cells

Metals known to have toxic effects on exposed individuals (Aluminum (Al), Cadmium (Cd), Zinc (Zn) and lead (Pb)) were selected. Umbilical cord erythrocytes from normal newborns were incubated in isotonic media alone or with addition of Pb (20 microM), Cd, Zn or Al (concentration range: 20-250 microM). Red cells were then placed in media of diminishing tonicity, to measure cellular lysis and volume; the regression curves of percent lysis as a function of osmolarity were determined for each data set and the break points calculated. Resistance to lysis increased significantly in Pb treated cells whereas cells treated with the other metals did not differ from controls, even at concentrations ten times higher than that of Pb. Lead produced a reduction in cellular volume corrected by addition of quinidine (an inhibitor of potassium channels activation) to the cell suspension; on the other hand, quinidine did not modify the effect of lead on lysis sensitivity. These results suggest that the effect of lead on cell resistance to lysis might be mediated by changes in membrane structure. The other metals examined did not affect the variables studied.

Human red blood cells from prenatal hemopoiesis. Lithium flux (sodium dependent) asymmetry

In red cells from umbilical cord blood it has been referred the existence of lithium fluxes (contralateral sodium dependent) asymmetry. On account of the relevancy of this transport system in some pathologies it is pertinent the study of its kinetics to relate normal with pathological states in which it is affected. Lithium fluxes--contralateral sodium dependent were determined in N-ethylmaleimide treated neonatal red blood cells. Experimental data were fitted by simple Michaelis-Menten kinetics, finding Km and Vmax variables. It was shown the persistency of asymmetry. The independence of sulfhydryl groups (or the occultation of the groups involved to this inhibitor) could explain asymmetry persistence.