HUMAN RED-CELLS FROM PRENATAL STAGES OF HEMATOPOIESIS - LITHIUM FLUX COMPONENTS

Red cells from umbilical cord with increased lithium content were subm itted to different experimental conditions in order to study lithium f lux components. There appeared three components: First, an ouabain-sen sitive component, related to Na+ replacement with Li+ in the primary a ctive Na+/K+ transport system. The magnitude of this fraction is great er than in adults' red cells. Second, an outside sodium-dependent Liefflux fraction, corresponding to the Li+/Na+ countertransport system with V-max and K-m values of 0.1 (mmol/l cells . h) and 2.58 (mmol/l), respectively. The Na-0(+)-affinity for lithium efflux in this system is greater in neonatal than in adults' red cells. Third, a leak fracti on with an equal value to that reported in adults' red cells. Furtherm ore, the possible non-existence of a bumetanide-sensitive lithium flux fraction was shown in neonatal red cells