AJP - Renal Physiology, Vol 251, Issue 5 873-F878, Copyright © 1986 by American Physiological Society
Lactate increases potassium secretion by perfused rat kidney
M. Brezis, K. Spokes, P. Silva and F. H. Epstein
The effect of exogenous metabolic substrates on K+ secretion was evaluated
in the isolated perfused rat kidney in the presence of 2-deoxyglucose and
2-tetradecylglycidic acid to inhibit utilization of glucose and fatty acids
from endogenous sources. L-Lactate (15 mM) added to the perfusion medium
enhanced renal oxygen consumption (4.0 +/- 1.1 mumol X min-1 X g-1 vs. 2.0
+/- 1.0 without lactate) while decreasing fractional excretion of sodium
(19.3 +/- 2.4% vs. 47.3 +/- 1.8). L-Lactate markedly increased the
fractional excretion of K+ to 181 +/- 29% compared with 68 +/- 12% without
lactate (P less than 0.001). The poorly metabolized isomer D-lactate did
not alter these parameters. The addition of alpha-ketoglutarate only
slightly increased K+ excretion. In the absence of metabolic inhibitors and
in the presence of glucose (5 mM), L-lactate also increased K+ excretion
significantly more than did D-lactate (108 +/- 19% vs. 69 +/- 11, P less
than 0.02). At the end of 90 min of perfusion with L-lactate medium, K+
concentration in the perfusate dropped from 4.7 +/- 0.05 to 3.2 +/- 0.2
meq/liter (vs. 3.8 +/- 0.1 meq/liter with D-lactate, P less than 0.005)
without differences in glomerular filtration rate or sodium excretion.
L-Lactate appears to increase K+ secretion by preferential metabolic
stimulation of the distal tubule, a process that may help in vivo to
prevent hyperkalemia in lactic acidosis.
