Plasma esterase-1 (ES-1) activity in rats is influenced by the amount and type of dietary fat, and butyryl cholinesterase activity by the type of dietary fat.

In previous work, we studied, under conditions of ad libitum food consumption, the effect of amount and type of dietary fat on plasma esterase-1 (ES-1) and butyryl cholinesterase activity in rats. This was done by the isoenergetic replacement of dietary fat by carbohydrates or by another fat source. The observed change in enzyme activity could theoretically be determined by either the dietary omission or the addition or by the combination. In the present work, we studied under restricted feeding conditions the effect of supplemental energy in various forms to determine the effect of the supplement alone. Supplemental coconut fat, but not isoenergetic amounts of either glucose or casein, raised plasma ES-1 activity. None of these supplements influenced butyryl cholinesterase activity. In a second experiment, we demonstrated that the ES-1 enhancing effect of supplemental coconut fat also occurred with fish oil, whereas the stimulatory effects of olive oil and corn oil were less pronounced. Supplemental fish oil, but not the three other fats, significantly reduced the depression in butyryl cholinesterase activity. Plasma cholesterol concentration was negatively associated with butyryl cholinesterase activity, but was not related to ES-1 activity. The two esterases were not correlated with plasma triglyceride concentration. We conclude that both the amount and type of fat in the diet of rats have specific influences on plasma ES-1 activity and that butyryl cholinesterase activity is affected by the type of fat.