Pathogenesis of hyperphosphatemia in lactic acidosis: disparate effects of racemic (DL-) and levo (L-) lactic acid on plasma phosphorus concentration.

The mechanism(s) for the hyperphosphatemia associated with lactic acidosis is unknown. Experimental lactate-induced hyperphosphatemia appears to require acidemia because we have shown that prevention of acidemia with NaHCO3 obviates increases in plasma phosphorus concentration ([P]). Since the rate of lactate metabolism (by utilizing NAD or other mechanisms) might modulate transcellular movement of phosphorus, we assessed the plasma [P] response to 3-h infusions of DL-lactic acid versus L-lactic acid. The dog metabolizes primarily the L-moiety of DL-lactic acid (thereby consuming H+), so more L-lactic acid is needed to produce the degree of acidemia attained with DL-lactic acid. Group 1 (n = 6) mongrel dogs received 12 mequiv./kg DL-lactic acid; group 2 (n = 6) 12 mequiv./kg L-lactic acid, and group 3 (n = 7) 16-19 mequiv./kg L-lactic acid. Prior to acid loading, the plasma [P] and acid-base status of the three groups were similar. After 3 h, blood pH and [HCO3] and change from base line in plasma [P], in both milligrams per decilitre and percent, were as follows: group 1: 7.05 +/- 0.02, 9 +/- 2 mM, 1.9 +/- 0.4 mg/dL, 38 +/- 10%; group 2: 7.28 +/- 0.02, 18 +/- 1, 0.9 +/- 0.3, 17 +/- 6; group 3: 7.06 +/- 0.04, 12 +/- 1, 1.1 +/- 0.3, 26 +/- 10, respectively. Thus, there was a tendency for both infusion rates of L-lactic acid to increase [P] less than DL-lactic acid, suggesting the importance of other factors in addition to pH.(ABSTRACT TRUNCATED AT 250 WORDS)