Laktaatti

Laktaatti, or lactate in English, is the conjugate base of lactic acid and a common metabolite in humans and other animals. It exists mainly as the lactate anion in the body at physiological pH and is produced and utilized in many tissues. The chemical form most relevant to physiology is the lactate ion (C3H5O3−); lactic acid itself has the formula C3H6O3 and a pKa around 3.86.

Metabolism and transport: Lactate is produced from pyruvate by the enzyme lactate dehydrogenase (LDH) during anaerobic glycolysis, regenerating NAD+ needed for glycolysis. Lactate can be exported from cells via monocarboxylate transporters (MCTs) and transported to other tissues, including liver, heart, and brain, where it can be oxidized back to pyruvate or used for gluconeogenesis (Cori cycle).

Physiological role: Lactate is not merely a waste product; it serves as an energy substrate, a signaling molecule, and a carbon shuttle between tissues. Its production increases during intense exercise and under hypoxic conditions. Lactate clearance depends on liver and kidney function and the capacity of tissues to take up and metabolize lactate.

Clinical significance: Elevated blood lactate is a biomarker for tissue hypoxia, sepsis, shock, and certain metabolic disorders. High lactate levels can indicate impaired perfusion or mitochondrial dysfunction and are used to monitor critically ill patients. Severe lactate accumulation can contribute to acidosis, though lactate itself is not the sole driver of fatigue.

History and nomenclature: Lactic acid was first isolated in 1780 by Carl Wilhelm Scheele from sour milk. The term lactate refers to the salts and the metabolically active lactate ion, and is widely used in physiology and medicine.