Urinary excretion of both D‐ and L‐lactate using a calf‐infusion model

Abstract

D‐lactic acidosis is recognized as a complication of gastrointestinal diseases in humans and ruminants. Absorbed D‐lactate can be excreted via the kidney; however, competition between D‐ and L‐lactate in the renal mechanisms may effect its elimination. The objective of this study was to measure D‐ and L‐lactate clearance in a calf infusion model. Five calves (age 14–31 days, weight 59 ± 8 kg) were infused with DL‐ and L‐lactic acid (300 mmol/L, 2 mL/kg/h for 8 hours) in a randomized cross‐over design. Calves were fitted with intravenous catheters for infusion and blood collection, and with suprapubic bladder catheters for urine collection. Samples for blood gas analysis, serum and urine D‐ and L‐lactate concentration, urine volume and serum and urine creatinine were collected every 2 hours for 24 hours. D‐ and L‐lactate clearances were calculated for each 2 hour interval and compared to creatinine clearance. With infusion of DL‐lactate, average serum D‐lactate concentration at steady state was 2.9 ± 1.6 mmol/L (range 1.8–5.7 mmol/L), and average urine D‐lactate concentration was 4.0 ± 1.7 mmol/L. Average D‐lactate clearance during steady state was 7.4 ± 3.4 mL/min. Percent excretion of infused D‐lactate increased during the 8 hour infusion, with minimum and maximum excretion averaging 0.6 ± 0.1% and 10.4 ± 4.4%. L‐lactate clearance could not be calculated, likely due to rapid metabolism of infused L‐lactate. Therefore, L‐lactate elimination is more efficient than D‐lactate since it can both be metabolized and excreted from the body. (Supported by NSERC Canada)