Role of fatty acids in regulation of phosphoenolpyruvate and citrulline synthesis in rabbit liver mitochondria.

In previous reports from this laboratory [ 1,2] we have shown that in guinea pig liver mitochondria there is a competition for energy between PEP and citrulline synthesis. Fatty acids are known to affect the intramitochondrial PEP* formation. Octanoate has been found to inhibit PEP production [3,4], while oleate results in a stimulation of this process [5,6] . In the present investigation the effect of octanoate and oleate on the production of PEP and citrulline has been studied in rabbit liver mitochondria. Data indicate that differential effects of fatty acids on PEP and citrulline synthesis under various metabolic conditions result from an alternation of NADH/NAD ratio and the mitochondrial phosphate potential, respectively. These observations led to suggest a possible role of fatty acids in the regulation of both gluconeogenesis and urea cycle in the rabbit liver. A prelimina~ report of some of findings presented in this paper has been made [7] .