The determination of vitamin A and some aspects of its distribution, mobilization and transport in health and disease.

The author has attempted to evaluate some of the methodology currently in 
use or suggested for the routine determination of vitamin A in 
blood and tissues. Special consideration is given to extraneous factors which 
can cause erroneous results in fluorometric analyses. A review of the 
older and current literature on the distribution of vitamin A in 
tissues is presented. Special consideration is given to the uptake of 
vitamin A by the liver and its storage in hepatocytes and 
Kupffer's cell and in subcellular organelles. Data on the concentration of 
vitamin A in the liver of victims of accidental death and 
the effect of diseases of several etiologies are presented. The mechanism 
by which liver stores of retinyl esters are mobilized and released 
to the plasma remains obscure. Considerable information has been gained recently 
on the mechanism by which retinol is transported in blood. Studies 
leading to the isolation and characterization of retinol transport proteins are 
summarized. The metabolism of retinol binding protein in health and in 
disease, especially in cystic fibrosis, is discussed. Finally, some factors of 
importance to the interpretation of plasma levels in terms of vitamin 
A are reviewed. Special attention is given to the effect on 
plasma levels of retinol and the retinol transport proteins of periods 
of rapid growth (correlations with age) and the influence of dietary 
adequacy on the distribution of plasma levels of the vitamin. 