Turnover of 131I‐human spleen ferritin in plasma

Abstract

Human spleen ferritin was labelled with ¹³¹I and injected into two normal men. The labelled ferritin left the plasma rapidly. The experimental clearance curve could be fitted with accuracy into two single exponential functions. The first component, T_1/2= 9 min, accounted for the clearance of about 90% of the labelled ferritin. Surface counting showed uptake of ¹³¹I by the liver but not by the spleen. Such a rapid plasma turnover is similar to that found after injection of tissue ferritins into experimental animals but contrasts with the slow turnover previously found for ¹³¹I-labelled human plasma ferritin. Differential clearance of isoferritins from the plasma is an important factor explaining the biochemical and immunological differences between tissue and plasma ferritins.