In addition to skeletal muscle, this metabolic cooperation was also demonstrated between other extrahepatic tissues and liver. Indeed, like the glucose-alanine cycle, the glucose-lactate cycle is active between the liver and all those tissues that do not completely oxidize glucose to CO2 and H2O, in which case pyruvate for conversion to lactate or, by transamination, to alanine would lack (see below).
In addition to skeletal muscle cells, examples of cells that continually produce lactic acid are red blood cells, immune cells in the lymph nodules, proliferating cells in the bone marrow, and epithelial cells in the skin.
Note: skeletal even at rest, muscle produces lactate although at low rate. From a biochemical