L-Lactate as a source of carbon for fatty acid synthesis in adult and foetal sheep.

The contribution of carbon from acetate, glucose and L-lactate to fatty acid synthesis has been compared in adipose tissue from adult and foetal sheep. Adipose tissue slices were incubated with mixtures of acetate, glucose and L-lactate at concentrations found in sheep blood. Under these conditions acetate, glucose and L-lactate contributed 95, 2 and 3%, respectively, of the C2 units used for fatty acid synthesis in adipose tissue slices from adult sheep. In contrast, acetate, glucose and L-acetate provided 50, 17 and 33%, respectively, of the C2 units for fatty acid synthesis in adipose tissue slices from foetal lambs (about 30 days prior to birth). The contribution of acetate and L-lactate carbon to fatty acid synthesis varied with their concentrations over the normal physiological range at both ages. We conclude that L-lactate is normally a minor source of carbon for fatty acid synthesis in the adult sheep but is an important source in foetal lambs.