MODULATION OF BINDING CHARACTERISTICS OF PERIPHERAL BENZODIAZEPINE RECEPTORS IN VITAMIN-A-DEFICIENT GUINEA-PIG LUNG

Both vitamin A and peripheral benzodiazepine receptors (PBRs) are invo lved in the control of cell proliferation and differentiation. The obj ective of this study was to determine whether vitamin A deficiency cau ses any modulation in the binding characteristics of the PBR5. Forty-f ive weanling guinea pigs were divided into three groups (control, pair -fed control, and vitamin A-deficient). Vitamin A-deficiency status wa s achieved after 90 days of feeding. It caused atelectasis, hyperplasi a and metaplasia of alveolar epithelium, acute inflammation of the tra cheobronchial tree, and a significant increase in the number of alveol ar type II cells. In comparison to the control and pair-fed control gr oups, the lung of vitamin A-deficient animals had 40.6 and 42.8% less PER density, respectively. There was no significant difference in the equilibrium dissociation constant (K-D) of PBRs between the control an d the pair-fed control groups, whereas the K-D value was 77.7 and 60% higher in the vitamin A-deficient group than in the control and the pa ir-fed control groups, respectively. Furthermore, vitamin A deficiency caused a decrease in the binding capacity of PBRs in both nuclear and mitochondrial fractions. These results may suggest a close functional relationship between vitamin A and PBRs.