Hardarson, Thorir, Jon O. Skarphedinsson, and Torarinn Sveinsson. Importance of the lactate anion in control of breathing. J. Appl. Physiol. 84(2): 411-416, 1998.The purpose of this study was to examine the effects of raising the arterial La and K⁺ levels on minute ventilation (E) in rats. Either La or KCl solutions were infused in anesthetized spontaneously breathing Wistar rats to raise the respective ion arterial concentration ([La] and [K⁺]) gradually to levels similar to those observed during strenuous exercise. E, blood pressure, and heart rate were recorded continuously, and arterial [La], [K⁺], pH, and blood gases were repeatedly measured from blood samples. To prevent changes in pH during the La infusions, a solution of sodium lactate and lactic acid was used. Raising [La] to 13.2 ± 0.6 (SE) mM induced a 47.0 ± 4.0% increase in E without any concomitant changes in either pH or PCO₂. Raising [K⁺] to 7.8 ± 0.11 mM resulted in a 20.3 ± 5.28% increase in E without changes in pH. Thus our results show that La itself, apart from lactic acidosis, may be important in increasing E during strenuous exercise, and we confirm earlier results regarding the role of arterial [K⁺] in the control of E during exercise.