Renal salvage of haemoglobin iron

Recycling of radioiron by renal tubular cells was studied in rats labelled by the i.v. injection of free 59Fe-Hb. Within 24 h, most of the renal radioactivity has been transferred from Hb to cellular ferritin and haemosiderin. Between day 1 and 14 of the study, urinary loss of radioactivity was less than 1% and most of the reduction in renal radioactivity represented transfer of renal iron into the circulation. An unexpected flexibility in the ability of rat kidney to recycle iron into the body has been found ranging from 13% in hypertransfused rats to 70% in bled animals. The high rate of renal iron transfer in bled animals was maintained under experimental conditions simulating chronic haemoglobinuria when most of the Hb removed by bleeding has been reinjected in the form of soluble Hb. Thus, epithelial cells in rat kidney as well as in the gut, appear to be able to transport iron with a much greater efficiency than in man, thereby contributing to the supply of iron for the rapid rates of growth and reproduction characteristic of this animal species.