Balance of net base in the rat: adaptation to and recovery from sustained hypercapnia.

Net base and mineral balances were evaluated in a group of male 350 g Wistar rats exposed to 10% carbon dioxide in air for 10 days with a view to identifying the source of net base subject to retention during renal compensation of sustained respiratory acidosis. In response to hypercapnia, the rate of renal net acid excretion rose but insignificantly. However, a rise in whole body net base concentration from about 215 mmol/kg to about 250 mmol/kg came about by ongoing gastrointestinal absorption in the weight-losing animal, absorbed net base being distributed to extracellular and non-extracellular compartments of the body, presumably including bone. During an 8-day recovery period, a small decrement in whole body net base concentration was observed.