Differential turnover of rat liver isoferritins.

Rat liver ferritins consist of families of isoferritins fashioned from different proportions of two subunit types, H and L. Iron administration alters both the absolute and the relative amounts of these isoferritins through an increase in L-rich forms. This phenotype change represents preferential synthesis of L-rich isoferritins together with a faster degradation of H-rich isoferritins. The turnover rates of isoferritins in the same liver are markedly different and vary progressively with subunit composition. The H and L subunits in individual isoferritins appear to turn over at similar rates, suggesting that the various isoferritins are degraded as intact shells rather than through exchange and degradation of subunits.