Entry of Ferritin into Human Red Cells during Hypotonic Haemolysis

A NUMBER of small molecules have been shown to enter red cells during hypotonic haemolysis. The membrane has been shown to be permeable to ATP (refs. 1, 2) and ghosts containing a number of organic compounds of metabolic interest, such as adenosine, cytidine, ATP and G6P, have been prepared 3 . The entry of dextran, with molecular weights from 10,000 to 250,000, into the red cell has been reported 4 , and albumin labelled with iodine-131 and haemoglobin labelled with iron-59 have been introduced into ghosts, and it was shown that these molecules could enter the cell only during haemolysis 5 . The red cell membrane is normally impermeable to these molecules, as well as to haemoglobin, and becomes impermeable again after release of haemoglobin, and so it is possible that the foreign molecules make their entry through the same channels which allow the escape of haemoglobin. The diffusion radius of haemoglobin is not less than 32 AU (ref. 6) and so the pores in the slightly stretched membrane of the haemolysing cell must be at least 64 AU in diameter during release of haemoglobin.