It is already clear that when ketone bodies were infused in this experiment, the concentration of ammonia in the urine must have decreased because of extrinsic metabolic processes, including those involving glutamine. In fact, it is easy to get confused about causal effects in this regard, so metabolic conversions and their significance should be carefully considered. For example, when ketone bodies are infused into the body, the concentration of ammonia in the urine and blood drops rapidly (up to 60%). At the same time, the synthesis of glutamate in the blood requires an excess of ammonia, which is consumed by alpha-ketoglutarate.
Thus, the absence of free ammonia due to the suppression of ammonia genesis affected glutamine synthesis as well, and for this reason, its renal arteriovenous difference was not noticeable. Consequently, only a small amount of glutamine was produced in the body, and the ketone body administered not as a pure acid had no effect on changes in urine and blood pH, and thus hepatic hemodynamics were not subject to severe acidic changes. Putting this together, there was no difference in glutamine production because the ketone body stimulated ammonia genesis, but there was no significant change in the acidity of the medium; glutamine continued to be produced, but the differences in its concentrations were not significant.
In contrast, infusion of beta-hydroxybutyrate into the left renal artery resulted in a sharp decrease in ammonia genesis, as previously shown. The ketone body could not positively influence ammonia production because ammonia was expended to convert glutamine from glutamates. In this context, it is interesting to mention the study by Plaitakis et al., which clarified that the enzyme glutamate dehydrogenase, which catalyzes the reversible conversion of glutamate to alpha-ketoglutarate, is associated with ammonia metabolism. In other words, suppression of this conversion (or its reversible process) affects ammonia genesis in the kidneys. In short, the drastic decrease in ammonia genesis is a response to the suppression of glutamate dehydrogenase.