Effects of Excess Methionine Ingestion on Hepatic Phosphate, Adenine Nucleotides and Free Amino Acids in the Rat

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Abstract
Adult male rats were force-fed either a single dose of 200 mg of dl-methionine or an amino acid mixture with the pattern of casein. The animals were anesthetized with pentobarbital at 0, 1.5, 3 and 4 hours after intubation, and samples of liver were removed by a freeze-clamping technique at 0, 15 and 30 seconds of ischemia. Hepatic ATP, ADP, AMP, Pi, glucose-6-phosphate, glucose and certain nitrogenous compounds as well as plasma glucose were determined. After methionine was given by intubation, hepatic methionine and glutathione increased severalfold within 1.5 hours; cystathionine showed a transient rise at this time but returned to normal at 3 and 4 hours, when taurine was progressively increasing. Several nonessential amino acids decreased, suggesting that they may be utilized for energy. Methionine forcefeeding did not modify the concentration of hepatic adenine nucleotides and probably did not change their turnover, as estimated from changes during ischemia. The level and production of Pi during ischemia was increased however. After force-feeding the amino acid mixture, hepatic methionine, cystathionine and taurine were unaffected, and glutathione increased only at hours 3 and 4; glycine and threonine were elevated by 1.5 hours. Hepatic adenine nucleotides, inorganic phosphate and glucose were not significantly affected by the feeding of amino acids by intubation.