effects of dietary eritadenine on the liver microsomal delta6desaturase activity and its mrna in rats eritadenine a hypocholesterolemic factor of lentinus edodes mushroom has a wide range of effects on lipid metabolism such as an increase in the liver microsomal phosphatidylethanolamine pe concentration a decrease in the liver microsomal delta6desaturase activity and an alteration of the fatty acid and molecular species profile of liver and plasma lipids in this study the timedependent effects of dietary eritadenine on several variables concerning lipid metabolism were investigated in rats to clarify the sequence of metabolic changes caused by eritadenine with special interest in the association of the liver microsomal phospholipid profile and the activity of delta6desaturase the effect of dietary eritadenine on the abundance of mrna for delta6desaturase was also investigated when the time required for a halfchange of variables was estimated during the first 5 days after the change from the control diet to the eritadeninesupplemented 50 mgkg diet the change rates of the variables were fastest in the following order alteration of the liver microsomal phospholipid profiledecrease in liver microsomal delta6desaturase activityalteration of the fatty acid and molecular species profiles of microsomal and plasma phosphatidylcholine pcdecrease in the plasma cholesterol concentration there was a significant correlation between the delta6desaturase activity and liver microsomal pe concentration but not pc concentration or the proportion of pc and pe or the pcpe ratio the suppression of delta6desaturase activity by dietary eritadenine was accompanied by a significant reduction in the abundance of mrna for the enzyme these results suggest that dietary eritadenine might suppress the activity of liver microsomal delta6desaturase by altering the microsomal phospholipid profile as represented by an increase in pe concentration and that the effect of eritadenine is mediated by the regulation of gene expression