Turnover of Cyclic Adenosine-5´-Monophosphate Is Elevated in Skeletal Muscle of Vitamin E-Deficient Rabbits

Abstract

Two sets of experiments were performed to investigate the nonantioxidant functions of α-tocopherol. Eighteen rabbits in the first set and 48 rabbits in the second set were equally divided into three groups. The first group received a basal tocopherol-deficient diet supplemented with all-rac-α-tocopherol for 3 wk and the second group was fed the basal diet. The third group received vitamin E supplementation for 1 wk after 2 wk of consuming a tocopherol-deficient diet. In the first set of animals, skeletal muscle concentration, metabolism and turnover of various adenine nucleotides were measured by incubating the muscles of the three groups with [8-3H]adenine. The second set of experiments investigated in vivo concentration of various adenine nucleotides before incubation with radioactive substrate and quantity of newly formed adenine nucleotides after incubation with four different specific radioactive substrates: [8-14C]ATP; [8-14C]cAMP; [8-14C]5´AMP and [8-14C]adenosine. The results expressed per milligram of DNA were compared between the tocopherol-supplemented and tocopherol-deficient rabbits. Cyclic-AMP concentration (measured after a 2-h incubation with [8-3H]adenine) was lower and 5´-AMP concentration was very high in the tocopherol-deficient rabbits. The results of incorporation studies indicated that the turnover of ATP + ADP, cAMP, 5´-AMP and adenosine was higher in the tocopherol-deficient rabbits. Administration of tocopherol to tocopherol-deficient rabbits restored the turnover of cAMP to nearly normal values. These observations provided new insights concerning nonantioxidant functions of α-tocopherol.