RETINOID METABOLISM IN HUMAN-LEUKOCYTES

Leucocytes from subjects from 0 to 80 years old were separated into mo nonuclear and granulocyte fractions and the retinoids and retinoid-bin ding fractions were examined. Both leucocyte fractions were found to c ontain retinol, retinoic acid and an additional retinoid; retinoic aci d comprised 40% of retinoids in some samples. The protein fractions co ntaining retinoids included a 200 kDa protein and several 14-18 kDa pr oteins. Plasma concentrations of retinol changed little with increasin g age. In contrast, leucocyte concentrations of retinoids and retinoid -binding proteins increased quadratically with age. However, in granul ocytes from young children retinoids were almost undetectable.