The stimulation by glucagon of both ureogenesis and gluconeogenesis has been known for some years [1, 2]. Recently Yamazaki reported that pretreatment of the rats with glucagon yields mitochondria having (i) An increased phosphorylation rate [3](ii) An increased rate of citruline synthesis [4](iii) An enhanced ATPase activity in presence of uncoupler and an increased rate of K’uptake [5]. Garrison and Haynes [6] in their description of the hormone-induced stimulation of pyruvate carboxylation concluded that changes of mitochondrial content did not appear to account for the effect, which they attributed to an increased uptake and metabolism of pyruvate.

The results presented here show that the stimulatory effect of both glucagon and cyclic AMP (CAMP) on ureogenesis and gluconeogenesis in isolated rat liver cells was accompanied by an increase of the mitochondrial ATP/ADP ratio which consequently furnishes more energy for the mitochondrial steps of these two processes. Higher rates of citrulline production in liver mitochondria isolated from rats pretreated with glucagon or CAMP were associated with a raised mitochondrial ATP content and an enhanced adenine nucleotide translocase.