Guest guest Posted January 1, 2008 Report Share Posted January 1, 2008 It is important to distinguish between lactate and lactic acid -- some folks use the terms interchangeably and they are not the same. Best, Bill Black Cumberland Foreside, Maine =================================== Re: Body pH, effect on training Ralph, regarding lactic acid cycle, there is some stuff which I'd like to draw your attention on: - recent studies has shown that lactate is produced even when enough 02 exist in the system , suggesting that lactate is a key element in glycolisis regulation. In fact the mitochondria readily take both monocarboxilates . - has shown that lactate is actively oxidized in muscles. As much as 75% of lactate is oxidized during exercise, with only 25% percent being transported to liver to enter Cori cycle. - above is done through cell-cell shuttles (as for example from a glycolytic fiber to an oxidative fiber) , or intracelular shuttles. It was shown by that mitochondria contain lactate dehydrognease enzyme, and can oxidize lactate. Those 3 points shows that the 2 glycolitic pathways may after all not be so bluntly separated as believed until last years, by the end product of glycolisis. - I agree that there is a debate regarding the degree in which H+ buildup will impair exercise. And that probably is not as important as believed. However it is clear that during exercise pH will drop in the cytosol, at the site of glycolisis. Before the main pH HCO3- buffer can deal with this, the pH must be regulated at site. Here protein buffers are very important. I believe there existed studies which correlated histidine bipeptides with buffer capacity of the muscles. Therefore we cant overlook the importance of protein buffers. Dan Partelly Oradea, Romania > > > > > Ralph, > > > > Since MMA performance relays on anaerobic > > glycolisis, I believe the > > most important buffering capacity for performance is > > intramuscular > > buffering capacity. This is the site where acidosis > > may impair > > glycolytic speed, and affect muscle contraction (Ca2 > > - tropnonim ) > > interactions, and therefore rapidly impair > > performance. This is why > > I referred histadine bipepetides as very important > > buffering agents in > > this case. > > > > The issue talked, IMO, is not " altering " the body > > pH, but about > > availability of buffers of ***the site*** of > > anaerobic glycolisis, > > resulting in the most effective and rapid way in > > maintaining the pH. > > I.e talking about how buffering capacity in muscles > > can be > > **increased**. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 1, 2008 Report Share Posted January 1, 2008 If they are not the same how about you tell everybody how they are different Bill. Chad Scheitel, MA, CSCS Minneapolis, MN --- Black wrote: > It is important to distinguish between lactate and > lactic acid -- some folks use the terms > interchangeably and they are not the same. > > Best, > Bill Black > Cumberland Foreside, Maine Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 The difference is: Lactate: a chemical compound that is a salt or ester of lactic acid. Lactic Acid: a colorless organic acid produced by muscles. Best, Bill Black Cumberland Foreside, Maine Re: Lactic acid and lactate? If they are not the same how about you tell everybody how they are different Bill. Chad Scheitel, MA, CSCS Minneapolis, MN --- Black > wrote: > It is important to distinguish between lactate and > lactic acid -- some folks use the terms > interchangeably and they are not the same. > > Best, > Bill Black > Cumberland Foreside, Maine Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 Colleagues, This is correct, with one caveat: muscle glycolysis actually produces pyruvic acid. Lactate accumulation tends to result when glycolytic activity exceeds mitochondrial capacity to oxidize the end-product. At physiological pH, lactic acid dissociates into lactate and a hydrogen ion. Intracellular pH is ~7.0 at rest, but can approach 6.1 in FT fibers, so it's anybody's guess how much dissociation actually occurs in the working tissues. Regards, Plisk Excelsior Sports • Shelton, CT www.excelsiorsports.com Prepare To Be A Champion! ====================== Black wrote: The difference is: Lactate: a chemical compound that is a salt or ester of lactic acid. Lactic Acid: a colorless organic acid produced by muscles. ========================== Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 Black wrote: <<<It is important to distinguish between lactate and lactic acid -- some folks use the terms interchangeably and they are not the same.>>> **** You are correct in pointing out that lactate and lactic acid are not the same. As I pointed out in my post, lactate is a salt which is the result of substituting the H ion in lactic acid for Na or K. However, the terms are often used interchangeably because it is very difficult to measure Lactic acid whereas Lactate is easily measured in the blood. The Lactate production mirrors the production of lactic acid. Lactate in the blood rises in proportion to the production of Lactic acid. As long as there is enough bicarbonate in the blood to accept the H ion from the lactic acid, lactate will be formed from the lactic acid and the lacic acid level in blood is very low or immeasrueable. There are however medical conditions in which the body's bicarbonate load is inadequate and lactic acidosis does occur. This is generally a life threatening condition. Ralph Giarnella MD Southington CT. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 Plisk wrote: Colleagues, <<<This is correct, with one caveat: muscle glycolysis actually produces pyruvic acid. Lactate accumulation tends to result when glycolytic activity exceeds mitochondrial capacity to oxidize the end-product. At physiological pH, lactic acid dissociates into lactate and a hydrogen ion. Intracellular pH is ~7.0 at rest, but can approach 6.1 in FT fibers, so it's anybody's guess how much dissociation actually occurs in the working tissues.>>> ****** You make an excellent point. It is important in this discussion to realize that the FT fibers (IIb) have very few mitochondria. The chemical reactions which convert pyruvic acid to pyruvate and allow it to enter the Krebs cycle for further production of ATP reside within the mitochondria. The fibers which are in most abundance in power sports and come into play with maximum intensity are the FT (IIb) fibers which have very little capacity to metabolize pyruvate resulting in high levels of lactic acid to accumulate within the muscle. The Lactate is formed from lactic acid outside the muscle in the blood. During maximum contraction the blood vessels are compressed by the muscles so very little blood reaches the muscles which in turn prevents the removal of lactic acid into the blood stream. The intramuscular buffers obviously are limited in how many H ions they can accept and as a result the pH of the muscle drowps very low forcing cessation of further activity. Most the the chemical reactions are pH dependant. The type IIa FT and Type I (slow twitch fibers) have significantly more mitochondria than the FT (IIb). These are the muscle fibers which come into play with efforts that last longer than 30-40 seconds. Ralph Giarnella MD Southington CT Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 What is your opinion on lactate shuttles (shuttling from a FT fiber for example to a ST fiber, or shuttling lactate into mitochondria to be oxidized when conditions become favorable )as described by ? And generally , on the fact that mitochondria appears to be able to readily take lactate (and not only pyruvate), and oxidize it ? And another question, what is your opinion on the debilitating effects of H+ buildup ? Respectfully Dan Partelly Oradea, ROmania > The difference is: > Lactate: a chemical compound that is a salt or ester of lactic acid. > Lactic Acid: a colorless organic acid produced by muscles. > > ========================== > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 Why do you say that lactate is only formed only in consequence of lactic acid being shuttled in blood ? It will dissociate very well before. Lactate ions will exist. There is no need for the acid to reach blood to give birth to lactate ions. This I think is very clear. Dan Partelly Oradea, Romania > Colleagues, > > <<<This is correct, with one caveat: muscle glycolysis actually produces pyruvic acid. Lactate accumulation tends to result when glycolytic activity exceeds mitochondrial capacity to oxidize the end-product. > > At physiological pH, lactic acid dissociates into lactate and a hydrogen ion. Intracellular pH is ~7.0 at rest, but can approach 6.1 in FT fibers, so it's anybody's guess how much dissociation actually occurs in the working tissues.>>> > > ****** > You make an excellent point. It is important in this discussion to realize that the FT fibers (IIb) have very few mitochondria. The chemical reactions which convert pyruvic acid to pyruvate and allow it to enter the Krebs cycle for further production of ATP reside within the mitochondria. > > The fibers which are in most abundance in power sports and come into play with maximum intensity are the FT (IIb) fibers which have very little capacity to metabolize pyruvate resulting in high levels of lactic acid to accumulate within the muscle. The Lactate is formed from lactic acid outside the muscle in the blood. > > During maximum contraction the blood vessels are compressed by the muscles so very little blood reaches the muscles which in turn prevents the removal of lactic acid into the blood stream. The intramuscular buffers obviously are limited in how many H ions they can accept and as a result the pH of the muscle drowps very low forcing cessation of further activity. Most the the chemical reactions are pH dependant. > > The type IIa FT and Type I (slow twitch fibers) have significantly more mitochondria than the FT (IIb). These are the muscle fibers which come into play with efforts that last longer than 30-40 seconds. > > Ralph Giarnella MD > Southington CT > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 2, 2008 Report Share Posted January 2, 2008 Hi Dan, There is abundant evidence that PY-LA clearance/oxidation is facilitated by shuttling lactate between sites of production (in both fiber types) and consumption (especially in type I fibers). This mechanism seems to allow oxidative metabolism to buffer glycolysis to some extent while increasing energy yield, and its effectiveness depends on VO2max and pyruvate-lactate concentration. My understanding is that the mitochondria oxidize PY. LDH seems to be readily available, catalyzing the reaction in either direction depending on concentration of each substrate. But LA itself is not oxidized. Acid-base balance in the tissues is perturbed because of coupling between ATPase and glycolysis, not just H+ production itself. The evidence here seems to indicate that disturbances in excitation-contraction coupling and cross-bridge formation impair the muscle's mechanical properties and energetic efficiency. The specific mechanisms include depressed RFD, peak force, velocity, power and PCr repletion, as well as prolonged relaxation time. Years ago I had the good fortune to study under Dr. Bob Mazzeo at the University of Colorado (his prior experiences included working as one of Dr. ' associates at Cal Berkeley). Bob's understanding of muscle metabolism is masterful, and really helped clarify what's going on under the skin. Regards, Plisk Excelsior Sports • Shelton, CT www.excelsiorsports.com Prepare To Be A Champion! ================== Dan Partelly wrote: What is your opinion on lactate shuttles (shuttling from a FT fiber for example to a ST fiber, or shuttling lactate into mitochondria to be oxidized when conditions become favorable )as described by ? And generally , on the fact that mitochondria appears to be able to readily take lactate (and not only pyruvate), and oxidize it ? And another question, what is your opinion on the debilitating effects of H+ buildup ? ================================ Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 3, 2008 Report Share Posted January 3, 2008 Mr Plisk, thanks very much for your answer. It helps me to slowly build a complete image. Dan Partelly Oradea, Romania > > What is your opinion on lactate shuttles (shuttling from a FT fiber > for example to a ST fiber, or shuttling lactate into mitochondria to > be oxidized when conditions become favorable )as described by ? > And generally , on the fact that mitochondria appears to be able to > readily take lactate (and not only pyruvate), and oxidize it ? > > And another question, what is your opinion on the debilitating effects > of H+ buildup ? > > ================================ > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 3, 2008 Report Share Posted January 3, 2008 --- Dan Partelly wrote: > > Why do you say that lactate is only formed only in > consequence of > lactic acid being shuttled in blood ? It will > dissociate very well > before. I am a little puzzled when you say that lactic acid will dissociate very well before. Lactic acid occurs because pyruvic acid cannot enter the krebs cycle. In order for lactic acid to dissociate within the muscle cell (which I presume you are implying) it has to become a salt (Lactate). For that to occur it must have the Hydrogen ion removed and replaced with either a Na or K ion. There is a greater abundance of these ions present in the blood than in the cell. In order for this to happen within the cell there has to be an abundance of buffers present, either bicarbonate or others in the cell, which can accept these H ions. There are some, but obviously not enough of these intracellular buffers, otherwise one could continue maximum effort for many minutes rather that just seconds without developing profound intracellular acidosis. The very fact that intracellular pH drops from 7.0 to 6.1 tells us that there are insufficient buffers present take up all the H ions. It is true that lactate can eventually be metabolized in muscle cells as well as other cells however none of these cells do not have the capacity to store lactate. In order to metabolize Lactate the cell needs mitochondria wherein the lactate will be changed back to pyruvic acid in order to enter the Krebs cycle. However not all cells have an abundance of mitochondria. The largest and most powerful muscle cells (IIb) are distinguished from the Type I (ST) or Type IIa (FT oxidative) by lack of significant amounts of mitochondria. The Type IIb cells have just enough mitochondria to maintain metabolism during rest. In Power sports or very high intensity explosive sports the Type IIb fibers are the most abundant by far (in some athletes as much as 80-90% fibers are Type IIb) and there are very few if any Type IIa and a very small percentage of Type I fibers. Just enough to maintain basic non exercise activities. Even if the lactate were to remain within cells for a short time to wait for more " favorable conditions " , if the cells do not have enough mitochondria, they would be unable to metabolize all the lactate produced. However in this situation, when it does occur the lactate has to be converted back to pyruvic in order to enter the Krebs cycle (which only takes place within the mitochondria.) Therefore for the Type IIb cells it is important that they be able to transport the lactic acid to the blood for conversion to lactate. This lactate can then be taken up by other muscle cells (that have abundance of mitchondria) as well as heart cells ( which are loaded with mitochondria) and kidney cells. These cells will take up the lactate if there is an inadequate amount of glucose substrate available. During high intensity maximal effort the muscle cell can utilize utilize anywhere from 10-50 x the amount of glucose for the glycolytic process than it does at rest. There is a resultant enormous production of pyruvic acid. This has to immediately enter the krebs cycle or it is converted to lactic acid and finally to lactate. It is certainly more efficient for the lactate to return to the liver where it is re-converted into glucose, released into the blood stream and now is again available to enter the Type IIb muscle fiber and utilized once more in glycolysis. It is important to remember that the majority (85%) of the energy present in a molecule of glucose is still present in the lactate molecule. Only about 15% is used by the muscle for contraction. If the body lacked the ability to convert the lactate back to glucose and eventually make it back to the working muscle, the muscle would quickly run out of glycogen and have to call it quits for the day. Lactate is a way of recycling the unused energy resulting from a very ineffecient glycolytic pathway. If on the other hand you are talking about the High Intensity Endurance sports, for example cycling, the discussion takes a different direction. In these sports a great deal of training is directed to increasing the Oxygen transport mechanisms as well as mitochondrial density within the cells. Much of the training also goes into raising the " Lactate threshold " with all the concomitant buffering changes required. In these sports the Type I fibers are highly developed and represent the majority of muscle cells (in some athletes as much as 80-90%). Type IIb muscle cells are converted to endurance capable Type IIa fibers and therefore there is a marked decrease in the Type IIb fibers. As a result of these changes endurance increases at the expense of maximum power. Any weight lifter knows that in order to maximize power you stay away from endurance type training for this very reason. They want to maintain as many Type IIb fibers as possible and minimize the number of Type I and Type IIa fibers. Power athletes increase maximum power at the expense of endurance. >Lactate ions will exist. There is no need > for the acid to > reach blood to give birth to lactate ions. This I > think is very clear. > > Dan Partelly > Oradea, Romania > Just a biochemical terminology correction: Lactate is a salt and not an ion. Dan I am sure that there are still more questions than answers to this whole very interesting and very complex topic. To do this topic justice would take several chapters of a text book or perhaps an entire textbook. I personally believe that in order to understand the basic principles of training it is very important to know what biochemical, metabolic and physiological changes occur when we train. Different training regimens produce different types of biochemical, metabolic and physiological changes. Too often, I believe, trainers and coaches learn and teach certain training protocols without understanding the basic metabolic, biochemical and physiological changes that the protocols are designed to bring about. Looking forward to continuing this discussion. Ralph Giarnella MD Southington Ct USA Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 3, 2008 Report Share Posted January 3, 2008 Ralph, again, thank you for your comprehensive answer. When I talk about lactate being a ion, I have the following logic: (based on my very weak understanding of chemistry) when an acid is added to water , it will dissociate: CH3CH(OH)COOH <-> H+ + CH3CH(OH)COO- CH3CH(OH)COO- is a lactate ion. At physiological pH , the dissociation will be pretty strong. Even if pH will drop during glycolisis, a fair amount of dissociation will occur. Lactic acid pKa is 3.85, a pretty strong acid. I concur wholeheartedly on the necessity to know the biochemical, metabolic and physiological changes which occur with training. I am thrilled to the opportunity to learn from the very nice ppl on this list who share knowledge. Dan Partelly Oradea, Romania > > Just a biochemical terminology correction: Lactate is > a salt and not an ion. > > Dan I am sure that there are still more questions than > answers to this whole very interesting and very > complex topic. To do this topic justice would take > several chapters of a text book or perhaps an entire > textbook. > > I personally believe that in order to understand the > basic principles of training it is very important to > know what biochemical, metabolic and physiological > changes occur when we train. Different training > regimens produce different types of biochemical, > metabolic and physiological changes. > > Too often, I believe, trainers and coaches learn and > teach certain training protocols without understanding > the basic metabolic, biochemical and physiological > changes that the protocols are designed to bring > about. > > Looking forward to continuing this discussion. > > Ralph Giarnella MD > Southington Ct USA > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 3, 2008 Report Share Posted January 3, 2008 > > > > > Why do you say that lactate is only formed only in > > consequence of > > lactic acid being shuttled in blood ? It will > > dissociate very well > > before. > > I am a little puzzled when you say that lactic acid > will dissociate very well before. > > Lactic acid occurs because pyruvic acid cannot enter > the krebs cycle. > > In order for lactic acid to dissociate within the > muscle cell (which I presume you are implying) it has > to become a salt (Lactate). For that to occur it > must have the Hydrogen ion removed and replaced with > either a Na or K ion. > > There is a greater abundance of these ions present in > the blood than in the cell. > > In order for this to happen within the cell there has > to be an abundance of buffers present, either > bicarbonate or others in the cell, which can accept > these H ions. > > There are some, but obviously not enough of these > intracellular buffers, otherwise one could continue > maximum effort for many minutes rather that just > seconds without developing profound intracellular > acidosis. > > The very fact that intracellular pH drops from 7.0 to > 6.1 tells us that there are insufficient buffers > present take up all the H ions. > > It is true that lactate can eventually be metabolized > in muscle cells as well as other cells however none of > these cells do not have the capacity to store lactate. > **** Hi Dr Ralph, Aren't there enough K ions intracellular to form a salt with lactate ion?? Using the -Hasselbalch equation, we can find that in a PH ranging from 6,1-7 , lactate (or lactate ion ) is about 100-1000 times greater than lactic acid (pKa=3,85). Actually, a lactate (ion)- proton transporter removes the lactate from the cell. So, there has to be a great amount of dissociation within the cell. Am I missing sth? with respect, Chrisostomos Georgiou Ioannina, Greece Quote Link to comment Share on other sites More sharing options...
Guest guest Posted January 4, 2008 Report Share Posted January 4, 2008 Yes, I agree, the I beleive that lactate ions are shuttled out of the cell through a co-transporter protein , from MCT class (monocarboxilate transporter) , which takes a lactate ion , and a H+ ion . Probably excess H+ ions are further dealt with by the classic Na+/H+ exchanger. protein buffers play also a significant role at this level. Dan Partelly Oradea, Romania > > > > > > > > Why do you say that lactate is only formed only in > > > consequence of > > > lactic acid being shuttled in blood ? It will > > > dissociate very well > > > before. > > > > I am a little puzzled when you say that lactic acid > > will dissociate very well before. > > > > Lactic acid occurs because pyruvic acid cannot enter > > the krebs cycle. > > > > In order for lactic acid to dissociate within the > > muscle cell (which I presume you are implying) it has > > to become a salt (Lactate). For that to occur it > > must have the Hydrogen ion removed and replaced with > > either a Na or K ion. > > > > There is a greater abundance of these ions present in > > the blood than in the cell. > > > > In order for this to happen within the cell there has > > to be an abundance of buffers present, either > > bicarbonate or others in the cell, which can accept > > these H ions. > > > > There are some, but obviously not enough of these > > intracellular buffers, otherwise one could continue > > maximum effort for many minutes rather that just > > seconds without developing profound intracellular > > acidosis. > > > > The very fact that intracellular pH drops from 7.0 to > > 6.1 tells us that there are insufficient buffers > > present take up all the H ions. > > > > It is true that lactate can eventually be metabolized > > in muscle cells as well as other cells however none of > > these cells do not have the capacity to store lactate. > > > > **** > Hi Dr Ralph, > Aren't there enough K ions intracellular to form a salt with lactate > ion?? > Using the -Hasselbalch equation, we can find that in a PH > ranging from 6,1-7 , lactate (or lactate ion ) is about 100-1000 > times greater than lactic acid (pKa=3,85). Actually, a lactate (ion)- > proton transporter removes the lactate from the cell. So, there has > to be a great amount of dissociation within the cell. Am I missing > sth? > > with respect, > Chrisostomos Georgiou > Ioannina, Greece > Quote Link to comment Share on other sites More sharing options...
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