1. Gluconeogenesis from lactate or from glutamine is inhibited by 90–100% by sodium quinolinate (1 mmol/l) or 3-mercaptopicolinate (150 nmol/l) in the perfused rat kidney. l-Tryptophan is not metabolized and is without effect.
2. Lactate uptake and glucose production are inhibited to the same degree by 3-mercaptopicolinate in the kidneys of well-fed or starved rats.
3. Inhibition of gluconeogenesis from glutamine (1 mmol/l) by 3-mercaptopicolinate is accompanied by 50% inhibition of ammonia production, and 34% inhibition of glutamine uptake, in the kidneys of acidotic rats. Ammonia production from glutamine was not inhibited in kidneys from non-acidotic rats.
4. It is concluded that the increased rate of gluconeogenesis from glutamine which occurs in acidotic rats is an essential and primary event regulating all of the increase in ammonia formation.