Effect of liver disease on the kinetics of lactate removal after heavy exercise

Summary

Recovery from heavy exercise requires clearance of lactic acid from the blood and body tissues. Although it has long been felt that the liver plays the major role in lactate removal, it has more recently been asserted that skeletal muscle plays the dominant role. We felt it relevant to this controversy to determine whether patients with liver dysfunction have slowed lactate removal following heavy exercise. Eight patients with alcoholic liver disease and 5 normal subjects were studied. Liver function was measured by the¹⁴C-aminopyrine breath test; the results were expressed as the rate of appearance of¹⁴CO₂ in the breath two hours after ingestion, as a fraction of the ingested¹⁴C dose (%·h⁻¹). Each participant exercised on a cycle ergometer for 7 min at a work rate which was moderately heavy for that subject (mean peak lactate=5.3 mmol·L⁻¹). During, and for 45 minutes after exercise, blood was drawn from a hand vein catheter. The time required for blood lactate to decrease halfway toward resting levels (t_1/2LA) was determined. Compared to the normal subjects and historical controls, seven of the patients had distinctly slowed lactate removal. The t_1/2LA was as long as 46 min (as compared to approximately 15 min seen normally). Further, among the patients the 2 h breath excretion of¹⁴C was well correlated with the rate constant of lactate removal (r=0.82,P<0.01). Four of the patients with severe liver dysfunction performed a second exercise test in which, instead of resting after heavy exercise, low level exercise was continued. The t_1/2LA of the averaged responses decreased by 29%. We conclude that liver disease slows lactate removal at rest. Lactate removal during continued exercise is less severely impaired.