Mechanism of development in hypoxia
The fundamental cause of lactic acid accumulation lies in impaired oxygen supply to peripheral tissues (hypoxia). Life-threatening conditions such as myocardial infarction, pulmonary embolism, or massive hemorrhage deprive cells of an adequate oxygen supply.
In response to oxygen deprivation, cells are forced to alter their energy metabolism. To meet basic energy demands, they urgently activate anaerobic glycolysis, a process of carbohydrate breakdown without oxygen participation. A byproduct of this emergency pathway is lactic acid. As a result, blood lactate levels spike sharply, and plasma pH drops below optimal values. This acidic environment is detrimental to most protein structures: it disrupts the spatial configuration of enzymes, ultimately leading to global disruptions in cellular metabolism.
Metabolic clearance of lactate
In a healthy body, lactic acid concentration is tightly regulated by the balance between its continuous production and removal rate (clearance). Lactate utilization proceeds via two main physiological pathways:
- Aerobic oxidation. With sufficient oxygen, molecules are broken down into end products: carbon dioxide ($CO_2$) and water ($H_2O$).
- Gluconeogenesis. Lactate acts as a crucial plastic substrate for generating new glucose molecules. This process occurs predominantly in liver tissues and is a key link in the Cori cycle.
Enzymatic and organ causes of imbalance
Lactic acidosis manifests when the mechanism of pyruvate and lactate utilization breaks down. In addition to tissue hypoxia and dystrophy, which stimulate excessive acid production, internal enzymatic and organ defects play a huge role:
- Hepatocyte pathology. Any large-scale damage to liver tissue (such as cirrhosis or severe toxic hepatitis) deprives the organ of the ability to efficiently capture lactate from the blood and convert it into glucose.
- Pyruvate dehydrogenase complex (PDH) dysfunction. This multienzyme complex is responsible for converting pyruvate to acetyl-CoA. If PDH is blocked due to hereditary mutations or severe hypovitaminosis (specifically, vitamin B1 deficiency), aerobic oxidation halts. Excess pyruvate inevitably turns into lactate.
- Gluconeogenesis enzyme defects. Hereditary anomalies of the proteins responsible for glucose synthesis make it impossible to use lactic acid as a building material.
- Citric acid cycle enzyme block. Decreased activity of the Krebs cycle (TCA cycle) enzymes also interrupts the aerobic oxidation pathway, shifting the reaction equilibrium toward acidification of the environment.
Briefly: answers to topical questions
Defects in which specific gluconeogenesis enzymes cause hereditary lactic acidosis?
Hereditary lactic acidosis is caused by defects in enzymes involved in glucose synthesis, particularly glucose-6-phosphatase deficiency.
Specific enzymatic disorders:
- Glucose-6-phosphatase — hereditary deficiency of this enzyme disrupts the process of gluconeogenesis.
These genetic defects in gluconeogenesis enzymes block the use of lactate for glucose synthesis. As a result of the imbalance between production and utilization, there is a pathological accumulation of lactic acid in the blood, leading to a drop in plasma pH below the optimum and the development of lactic acidosis.
What are the normal reference values for blood lactate levels and pH?
Normal reference values for lactate are up to 2 mmol/L, and for blood pH, 7.36–7.44.
Main parameters within normal limits:
- Lactate — up to 2 mmol/L (at rest, concentration is 1 mmol/L).
- Blood pH — ranges from 7.36–7.44.
In uncompensated lactic acidosis, these values are disrupted. Blood lactic acid levels rise to 5 mmol/L, while the pH drops to 7.25 and below, indicating acidosis.
To remember the causes of lactate accumulation, trace the fate of pyruvate: it either "suffocates" without oxygen (hypoxia), cannot "burn" due to PDH and TCA cycle breakdown, or cannot become glucose due to a diseased liver. The outcome is always the same — it turns into lactic acid.
Class and exam questions
Why does blood pH drop during hemorrhages and infarctions?
Due to impaired oxygen delivery, cells switch to anaerobic glycolysis, the end product of which is lactate. The accumulation of this acid lowers plasma pH.
How do liver pathologies provoke lactic acidosis?
When hepatocytes are damaged (cirrhosis, hepatitis), gluconeogenesis is suppressed — the liver loses the ability to utilize lactate for new glucose synthesis.
A deficiency of which vitamin can cause lactic acidosis?
Vitamin B1 deficiency disrupts the normal operation of the pyruvate dehydrogenase complex (PDH), blocking the aerobic oxidation of pyruvate.
What is the danger of a drop in pH for cells?
A drop in pH below the physiological optimum disrupts the conformation and activity of vital enzymes, leading to global cellular metabolism disorders.
What else to study on this topic
- Anaerobic glycolysis: biochemical reactions and enzymes
- Pyruvate dehydrogenase complex (PDH) and its regulation
- Gluconeogenesis from lactate (Cori cycle)
- The role of the Krebs cycle (TCA) in metabolite utilization
- Effect of vitamin B1 (thiamine) on energy metabolism
Master the entire topic in the "Biochemistry" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Lactic acidosis" and 3,616 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 115 video lessons on the subject
Other topics in the section "Carbohydrate Metabolism"
Free video lessons: biochemistryShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.