Hi Amadeus I apologize for not replying to your message http://maelstrom.stjohns.edu/CGI/wa.exe?A2=ind0302&L=paleofood&P=R5514 from last February - I was rather busy at the time, and I thought your questions required lengthy answers, so I kept postponing my reply indefinitely. Amadeus Schmidt <[log in to unmask]> wrote: >You are right, ammonia of course is very basic (pH11) not acidic. >Is (I?) misinterpreted Roland's paragraph about blood pH and protein beeing a >basic food item so that excreting ammonia would lower blood pH directely >(like the kidney can make the urin acidic until ph 3). I am not sure I understand what you were saying here. >It's like you said, ammonia is basic, but helps the kidney excrete more >acids. >However, the problem is (similar to my postulation) that ammonia production >can't be risen very much because it is so toxic (by "unsure" mechanisms, but >you mentioned some). I disagree with your statement about the upper bound on ammonia production: as I said in my post, http://maelstrom.stjohns.edu/CGI/wa.exe? A2=ind0302&L=paleofood&P=R5206 , due to its toxicity, ammonia is not produced in significant amounts anywhere except at the site of excretion, namely in the kidney. In particular, it does not have to be present in the blood in order to be excreted. >Indeed blood ammonia is very little - 10-40mmol/L, compared to urea >(~10-fold). Thanks god - considering it's toxicity. Yes, but this does no t imply your next statement: >I think that's the reason why additional 100g protein can *not* be excreted >as ammonia resulting in less blood acidity. >The metabolic swith shuts down >ammonia production at an early stage. The metabolic acid-base switch actually results (according to the source that I had given and that you found a great reading) in MORE ammonia production. (As I said in my post, which you probably did not read carefully, the main purpose of the switch is the gradual translocation of gluconeogenesis from liver to kidney as the liver capacity for urea production is approached or as rising blood acidity requires more ammonia production. Gluconeogenesis in liver and in kidney has different substrates - alanine resp. glutamine, thus ammonia needs to be produced in the first stage of gluconeogenesis only in kidney.) >For smaller amounts of protein - in the dimens ions like can be made to >ammonia and buffered by the blood - Rolands equation should work. As I have just explained, I don't agree with this. >Therefore the protein ceiling should be determined by the capacity to make >and excrete urea. Yes, except that Roland Rohde seems to say that protein ceiling is not absolute at all (since gluconeogenesis in kidney does not require urea production). You wrote that increasing fat intake itself would rise the >protein ceiling, due to "less need of gluconeugenesis and higher ketosis". You misquoted me here - I said "less need for gluconeogenesis IN LIVER due to higher ketosis and resultant acid-base metabolic switch". >But what occurs to say 100g amino acids which were eaten and cannot be built >into new tissue? I think (correct me if I'm wrong) that there is no way to >avoid gluconeugenesis for this extra protein . I think that is correct (at least for glucogenic amino acids). By with else pathway should >the body get rid of it, once it's eaten? > Gluconeogensis (in kidney). >More ketosis makes more ketone bodies and these are acidic. Yes. >This would even reduce the ammonia (and acid) excretion, because the >metabolic switch to urea occured earlier. Right? >If the trigger for the switch (from ammonia to urea) is indeed blood acidity >as you write, and not the level of ammonia, >then higher ketosis could rather lift the protein ceiling >because less ammonia is produced (less toxicity for the brain) - >if ammonia is the reason for rabbit starvation. > I do not understand your reasoning competely, but you obviously misunderstood the purpose of the metabolic switch: the direction of the switch is FROM alanine-urea TO glutam ine-ammonia. I was saying that higher ketosis implies higher blood acidity, and this in turn implies greater need for ammonia production (in kidney; ammonia reduces blood acidity although it is not present in blood - it simply enables excretion of acids in the kidney). I am running out of time - I'll try to answer the remaining questions as soon as I can. Regards Darko