Ventilatory adaptation to metabolic alkalosis in adult awake potassium restricted rats

The resting ventilation of awake rats, developing metabolic alkalosis as a result of sustained dietary potassium (K) restriction, was compared to that of age-matched controls. Extending the measurements over 17 weeks and using adult rats indicated, as soon as the third week, a significant progressive fall in the minute ventilation of low K rats, which previous studies limited to a single time determination did not consistently ascertain. The ventilatory adaptation observed in all groups, as well as the superimposed respiratory compensation to metabolic alkalosis in low K rats, resulted only from frequency changes. In both groups, the duration of inspiration was inversely correlated with the age of the animals. The duration of expiration was stable in controls but increased significantly with time in low K rats. According to these data, the respiratory compensation to K-depletion alkalosis in the rat is achieved only through an adjustment in the timing component of the control of breathing.