Depressed plasma retinol-binding protein (RBP) in cystic fibrosis (CF)

Abstract

Decreased plasma levels with normal or increased liver stores of vitamin A were reported previously in CF patients orally supplemented with water-miscible vitamin A. These findings suggested a defect in the mechanism by which vitamin A is transported from the liver in patients with CF. Plasma levels of RBP, the specific carrier protein for vitamin A, have been measured by radioimmunoassay in 69 samples from 49 CF patients and in 96 normal age-matched controls. Mean RBP levels (± SEM) in CF, 24.4 ± 1.3 μg/ml, were significantly (p < .001) lower than in normal controls, 37.3 ± 1.3 μg/ml. In normal children 14 years and under, plasma RBP and vitamin A levels showed a signification (p < .001) correlation with age; in contrast no age-related rise was observed in CF children of comparable age. Saturation of RBO with vitamin A was less than normal (p < .004), and the levels of plasma prealbumin (the protein normally complexed with RBP) were decreased (p < .001) in the CF group 15 years and older compared with controls. Depressed plasma RBP levels were not correlated with plasma G.O.T. or albumin levels. These results suggest that a defect in the hepatic production and/or secretion of RBP occurs in CF.