Tissue distribution of S-adenosylmethionine and S-adenosylhomocysteine in the rat. Effect of age, sex and methionine administration on the metabolism of S-adenosylmethionine, S-adenosylhomocysteine and polyamines

摘要

pThe tissue distribution of iS/i-adenosylmethionine, iS/i-adenosylhomocysteine, methionine adenosyltransferase and iS/i-adenosylhomocysteine hydrolase was explored in the rat. Also the effects of methionine administration on the accumulation of iS/i-adenosylmethionine, iS/i-adenosylhomocysteine and polyamines were studied in rat liver, brain and kidney. The tissue distribution of iS/i-adenosylmethionine, iS/i-adenosylhomocysteine, methionine adenosyltransferase and iS/i-adenosylhomocysteine hydrolase was similar in both sexes, and was only slightly changed with age. The specific activity of iS/i-adenosylhomocysteine hydrolase greatly exceeded that of methionine adenosyltransferase, and the concentration of iS/i-adenosylmethionine was higher than that of iS/i-adenosylhomocysteine in all tissues examined. However, the hepatic iS/i-adenosylmethionine/iS/i-adenosylhomocysteine ratio was dependent on food supply and on the age of the animal. No correlation was noticed between the activity of methionine adenosyltransferase and the concentrations of the adenosyl compounds in different tissues. Intraperitoneal administration of methionine resulted in a profound but transient increase in the hepatic concentrations of iS/i-adenosylmethionine and iS/i-adenosylhomocysteine. The concentration of iS/i-adenosylmethionine was elevated also in the brain during the first 2h after methionine injection. The rise of iS/i-adenosylmethionine concentration after methionine treatment could be diminished by simultaneous glycine administration. The results support the view that the rate-limiting factor of iS/i-adenosylmethionine synthesis is the tissue concentration of methionine. They further suggest that glycine iN/i-methyltransferase may have a regulatory role in the utilization of iS/i-adenosylmethionine in the liver./p