The current emphasis of this study is on problems of hormonal regulation of hepatic metabolism focussed on intracellular compartmentation of nitrogen metabolism, mitochondrial-cytosolic interaction and the mechanisms of transfer of hormonal signals. Methods have been developed for measuring intracellular gradients of pH and membrane potential in intact isolated hepatocytes from the distribution of weak acids and bases, and lipophilic ions. The method permits a distinction to be made between mitochondrial and plasma membrane potential difference and pH gradients. Using these methods acute effects of hormone addition on intracellular gradients of pH and membrane potential will be studied, as well as differences in these parameters in different nutritional states and in diabetes. Under similar conditions, effects of the hormonal status on the intracellular distribution of metabolites will be studied, using cell disruption techniques. These data will allow an assessment of the importance of intracellular pH gradients and membrane potential differences in the transfer of metabolic signals across the mitochondrial membrane.