Plasma vitamin A transport and visual dark adaptation in diseases of the intestine and liver

Quantitative analyses of plasma concentrations of retinol binding protein (RBP), prealbumin and total proteins were performed in normal subjects and in forty-two patients suffering from diseases of the intestine and liver. The visual dark adaptation ability (DAA) was also assessed. Reduction of DAA and of RBP and prealbumin levels was noted in patients with chronic liver disease and fat malabsorption. In sixty-eight patients with intestinal diseases the RBP concentration seemed to be reduced in relation to the degree and duration of steator-rhoea. Furthermore, inflammatory activity, as revealed by laboratory tests, markedly reduced the RBP level. Treatment with vitamin A increased the RBP and prealbumin concentrations and restored the DAA to normal in patients with malabsorption but normal liver function. In patients with liver disease reduced DAA and serum RBP values were not affected by vitamin A therapy. Only at RBP concentrations below half the normal was impairment of the dark adaptation observed, suggesting that serum RBP is a more sensitive indicator of vitamin A deficiency than measurement of dark adaptation.