Aspects of the Metabolism of Retinol-Binding Protein and Retinol

Abstract

Publisher Summary This chapter presents different aspects of the metabolism of retinol-binding protein (RBP) and retinol. RBP is not significantly decreased until the liver reserves of the vitamin are virtually abolished. The diminished concentration of RBP in plasma in manifest vitamin A deficiency reflects the impaired transport of retinol to the various tissues. The catabolism of RBP is probably greatly dependent on renal function, since a small fraction of free RBP exists in plasma although most is bound to prealbumin. The biological half-life of RBP was increased by about 50% in protein deficiency while the rate of synthesis was diminished to one-third of the normal value. The cellular accumulation of retinol is a temperature-dependent process. Incubations of the cells in the absence of oxygen or in the presence of metabolic inhibitors like sodium azide and EDTA did not change their ability to extract retinol from RBP. It is seen that the labeled RBP component exhibited a slower electrophoretic mobility than genuine RBP, which could complex with prealbumin. The low pH was chosen to minimize charge differences due to variable content of amide groups in the two forms of RBP.