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Kinetics of S-adenosyl-L-methionine in isolated perfused rat liver and its effects on microsomal enzyme activity
Abstract:
S-Adenosyl-L-methionine (SAMe) levels in liver tissue were reduced by 35% after isolation and washing of the organ. The apparent half-life of SAMe (1,75-25 microM) during liver perfusion was between 120 and 460 min; however the uptake of the labelled methyl group by hepatic tissue of fed rats was low (6%). This value increased to 12% in organs isolated from 24-hour fasted animals. Addition of SAMe to the perfusion medium increased tissue levels of ATP. Except for N-demethylation of aminopyrine and cytochrome c reductase, liver microsomal activity was not affected by treatment with SAMe either in vivo or/and in perfused liver.
Insights
S-Adenosyl-L-methionine (SAMe) levels decrease in isolated livers. SAMe supplementation boosts ATP, but hepatic uptake and microsomal activity show limited response in fed rats.
Area of Science:
- Biochemistry
- Hepatology
- Pharmacology
Background:
- S-Adenosyl-L-methionine (SAMe) is a crucial methyl donor in numerous metabolic pathways.
- Liver function and metabolic processes are sensitive to SAMe availability.
- Understanding SAMe dynamics in isolated perfused livers is vital for drug metabolism and liver disease research.
Purpose of the Study:
- To investigate the stability and uptake of S-Adenosyl-L-methionine (SAMe) in isolated perfused rat livers.
- To determine the effect of SAMe on hepatic ATP levels and microsomal enzyme activity.
- To assess the influence of nutritional status (fed vs. fasted) on SAMe metabolism.
Main Methods:
- Isolated rat liver perfusion technique.
- Measurement of SAMe levels and apparent half-life during perfusion.
- Assessment of methyl group incorporation from SAMe into hepatic tissue.
- Analysis of hepatic ATP content.
- Evaluation of liver microsomal enzyme activities (e.g., N-demethylation, reductase activity).
Main Results:
- Isolated and washed livers showed a 35% reduction in SAMe levels.
- The apparent half-life of SAMe ranged from 120 to 460 minutes.
- Hepatic uptake of labelled methyl groups from SAMe was low (6% in fed rats, increasing to 12% in fasted rats).
- SAMe addition to the perfusion medium elevated hepatic ATP levels.
- Most liver microsomal activities remained unaffected by SAMe treatment, except for aminopyrine N-demethylation and cytochrome c reductase.
Conclusions:
- Isolated perfused livers experience a significant decrease in SAMe levels.
- Hepatic SAMe uptake is limited, particularly in fed states, but enhanced by fasting.
- SAMe supplementation can increase hepatic ATP levels but has minimal impact on overall liver microsomal activity.
- These findings provide insights into SAMe's role and limitations in liver metabolism and potential therapeutic applications.