Hepatic VLDL production appears to be correlated with de novo fatty acid synthesis (lipogenesis). In this study lipogenesis was inhibited in vitro in order to establish an eventual direct effect on VLDL secretion. Hepatocytes from rats fed a standard diet were incubated with three triglyceride-rich lipoproteins: chylomicrons and VLDL obtained from rats fed a high-fat diet and VLDL obtained from rats fed a standard diet. The inhibition of lipogenesis (10 to 55%) was proportional to the concentration of the lipoproteins added. Chylomicrons and VLDL originating mainly from the intestine (prepared from fat-fed rats) inhibited lipogenesis more effectively than VLDL produced essentially by the liver (prepared from rats fed a standard diet). However the secretion of newly synthesized fatty acids in the medium did not decrease. When hepatocyte lipogenesis was inhibited by the addition of 1 mM oleic acid, total VLDL secretion (expressed as nmol of VLDL triglyceride/10(6) cells) was unchanged compared to control cells incubated without oleic acid. Our results suggest that hepatic VLDL secretion is not directly related to de novo fatty acid synthesis.