Immediate adaptation of the dog kidney to acute hypercapnia

Studies were performed to determine whether ammoniagenesis could adapt instantaneously to acidosis in the dog kidney. Following acute respiratory acidosis, renal glutamine extraction rose acutely in dogs with stable renal blood flow but did not change when the renal blood flow fell by more than 25%. Acute hypercapnia immediately increased renal ammonia production in both groups of dogs. The rate of both glutamine extraction and ammonia production in acutely hypercapnic dogs without hemodynamic changes was comparable to the rates observed in dogs with chronic metabolic acidosis. Furthermore, the renal metabolite profile observed in acute hypercapnia was similar to the pattern described in chronic metabolic acidosis, i.e., a marked fall in renal glutamate and alpha-ketoglutarate concentrations and a fivefold increase in malate and oxaloacetate concentrations. In the liver and muscle, acute hypercapnia induced no significant change in glutamine concentration but glutamate and alpha-ketoglutarate concentrations decreased. Our findings demonstrate that the dog kidney can adapt immediately to acidosis but that hemodynamic change may mask this adaptation.