IMPORTANCE OF THE LACTATE ANION IN CONTROL OF BREATHING

The purpose of this study was to examine the effects of raising the ar terial La- and K+ levels on minute ventilation (((V) over dot E)) in r ats. Either La- or KCl solutions were infused in anesthetized spontane ously breathing Wistar rats to raise the respective ion arterial conce ntration ([La-] and [K+]) gradually to levels similar to those observe d during strenuous exercise. (V) over dot E, blood pressure, and heart rate were recorded continuously, and arterial [La-], [K+], pH, and bl ood gases were repeatedly measured from blood samples. To prevent chan ges in pH during the La- infusions, a solution of sodium lactate and l actic acid was used. Raising [La-] to 13.2 +/- 0.6 (SE) mM induced a 4 7.0 +/- 4.0% increase in (V) over dot E without any concomitant change s in either pH or PCO2. Raising [K+] to 7.8 +/- 0.11 mM resulted in a 20.3 +/- 5.28% increase in ire without changes in pH. Thus our results show that La- itself, apart from lactic acidosis, may be important in increasing (V) over dot E during strenuous exercise, and we confirm e arlier results regarding the role of arterial [K+] in the control of ( V) over dot E during exercise.