Effects of age on renal function and enzyme activity in male C57BL/6 mice.
The activities of renal lactate and malate dehydrogenases, glutaminase, and Na-K-ATPase were determined in aging male C57BL/6 mice. Urine concentrating ability in these mice and renal response to metabolic acidosis were also studied. Total enzyme activities were measured in vitro in tissue homogenates from mice that were 120, 400, 500, 600, 700, and 800 days old. Urine concentrating ability was determined in these mice prior to sacrifice. Lactate and malate dehydrogenase activities decreased between 120 and 700 days with only male dehydrogenase activity increasing between 700 and 800 days. Age did not affect glutaminase or Na-K-ATPase activities and urine concentrating ability was decreased only at 700 days. Both urine ammonia excretion and renal glutaminase activity increased at 120 and 600 days in response to metabolic acidosis. However, only 5 of 12 animals tested at 600 days survived the acid stress for a full 7 days.