Hypoxic environments increase ventilation in animals. This helps to bring in more oxygen when environmental levels may be limited. With limited oxygen availability, the body turns to anaerobic metabolism, resulting in the production of lactate ions. These ions are known to indirectly stimulate breathing by lowering blood pH and were more recently discovered to directly stimulate the carotid body to increase breathing. For this reason, lactate ions are thought to be a ‘canary in the coal mine’ for hypoxic conditions in the body that can turn on mechanisms to restore oxygen concentrations.
In a new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, researchers wanted to know whether lactate ions could directly alter breathing in rainbow trout (Oncorhynchus mykiss) by targeting cells in the first gill arch, which is akin to a mammal’s carotid body. The researchers indeed found that administration of lactate increased ventilation and slowed down heart rate in trout likely by activating receptors in the gills that are also sensitive to serotonin.
Thomsen MT, Lefevre S, Nilsson GE, Wang T, Bayley M. Effects of lactate ions on the cardorespiratory system in rainbow trout (Oncorhynchusmykiss). American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 316(5): R607-620, 2019.