Haemoglobin Biosynthesis during in Vitro Maturation of the Rat Reticulocyte

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Abstract
Summary. The relationship of changes in cellular iron uptake, haem and globin synthesis in the maturing reticulocyte was studied during in vivo maturation of rat reticulocytes produced after phlebotomy. Cellular iron uptake and haem synthesis declined at a more rapid rate than did globin synthesis. During maturation there was a uniform loss of all ribosomal classes and [14C]leucine incorporation studies indicated a decreased time for polypeptide chain synthesis per polysome. These observations support the postulate that globin synthesis is controlled by the availability of haem, the latter in turn being dependent on the availability of iron. The following sequence of events in the maturing reticulocyte is suggested: first, there is a loss of the capacity of the reticulocyte to take up iron leading to cessation of haem synthesis. Depletion of available haem then results in either an accumulation of globin, which by a feedback mechanism suppresses further globin synthesis, or an activation of reticulocyte ribonuclease which breaks down the polyribosome‐mRNA complex, making further protein synthesis impossible.

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