Lactate Production of Mammalian Intestinal and Vascular Smooth Muscles Under Aerobic and Hypoxic Conditions

Abstract

Lactate liberation from thoracic aortas and intestinal smooth muscles of the guinea pig, rabbit and rat, as well as coronary arteries of the dog were determined under aerobic and hypoxic conditions (95% N₂ instead of O₂). In all smooth muscles tested, the lactate liberation was inhibited in the presence of oxygen, being known as the Pasteur effect. The rates of lactate release from guinea pig aortas and taenia caeci under hypoxia were approximately 10 times greater than those under aerobic conditions. The rate of lactate release from other smooth muscles tested were 3-4 times greater under hypoxic than aerobic conditions. The extent of Pasteur effect was not affected by a removal of adventitial layer from the rabbit aorta nor by the different size of the dog coronary arteries. These results suggest that taenia caeci and aortas of the guinea pig intrinsically possess a strong regulatory system in the glycolytic activity, being highly sensitive to the presence of oxygen.