Fatty acid and sterol synthesis by rat small intestine in vitro.

Slices of rat jejunum were incubated with [2(-14)C] pyruvate, [1(-14)C] acetate, or [3H]H2O to determine lipogenic activity. Under all conditions studied, pyruvate acted as a better precursor than acetate for fatty acid synthesis but not for the synthesis of sterol. Exogenous glucose significantly (P less than or equal to 0.05) increased the conversion of both pyruvate and acetate to fatty acids. By contrast fasting resulted in a decrease (p less than or equal to 0.05) in lipogenic activity. The highest levels of lipogenesis were observed when [3H]H2O + glucose at a concentration of 20 mM was used. From such experiments, the absolute rate of fatty acid synthesis in the tissue preparation was calculated: 734 +/- 54 nmoles acetyl units incorporated into fatty acids/g tissue/hr.