The effect of fatty acids and starvation on the metabolism of gluconeogenic precursors by isolated sheep liver cells.

Isolated liver cells prepared from fed sheep synthesize glucose from propionate at twice the rate observed with cells from starved animals. Addition of palmitate or palmitate + carnitine to incubations of liver cells from starved animals inhibited the rate of glucose synthesis with lactate as a precursor, but had little effect when propionate and pyruvate were substrates. Liver cells from fed and starved sheep synthesized lactate and pyruvate when incubated with propionate. Fatty acids inhibited this formation of lactate and pyruvate from propionate. It is proposed that the different responses of gluconeogenic precursors to fatty acids can be explained by the effect of reducing equivalents on the transport of carbon atoms across the mitochondrial membrane.