TRANSFERRIN-BOUND IRON UPTAKE BY THE CULTURED CEREBELLAR GRANULE CELLS

Excessive brain iron has been found in several neurodegenerative disea ses. However, little information is available about mechanism of iron uptake by different types of brain cells including neurons. In this st udy, transferrin-bound iron (Tf-Fe) accumulation in the cultured cereb ellar granule cell was investigated in vitro. After 5 days of culture, the cells were incubated with 1 mu M Of double-labelled transferrin ( I-125-Tf-Fe-59) af 37 degrees C for 60 min. The cellular Tf-Fe and tra nsferrin (Tf) uptake was analysed. The result showed (1) Tf uptake by the cells increased rapidly at the first 5 min, reaching its maximum a fter about 20 min of incubation; (2) Tf-Fe uptake kept increasing in a linear manner during the whole period of incubation; (3) the addition of either NH4Cl or CH3NH2, the blockers of Tf-Fe uptake via inhibitin g iron release from Tf within endosomes, decreased the cellular Tf-Fe uptake but had no significant effect on Tf uptake; (4) trypsin and unl abelled Tf-Fe inhibited the uptake rate of Tf-Fe as well as if. The re sults suggested that Tf-Fe transport across the membrane of this type of neuron, much like other mammalian cells, was mediated by Tf-TfR end ocytosis. Dysfunction of Tf or TfR would possibly lead to iron irregul ation in the brain and consequently cause damage to neuronal functions . (C) 1998 Elsevier Science ireland Ltd. All rights reserved.