AJP - Renal Physiology, Vol 245, Issue 2 142-F150, Copyright © 1983 by American Physiological Society
Metabolism and transport of L-glutamine and L-alanine by renal tubules of chickens
A. G. Craan, P. Vinay, G. Lemieux and A. Gougoux
The metabolism and cellular transport of 1 and 5 mM glutamine (Gln) and
alanine (Ala) and the metabolism of lactate (Lac) by renal tubular
fragments of normal and chronically acidotic chickens were studied. The
tubules were prepared by the collagenase digestion procedure and incubated
for 0-60 min with or without substrates. Acidosis increased 1 mM Gln
utilization from 1.14 to 1.74 and 1 mM Ala from 1.55 to 2.92 mumol X min-1
X g wet wt-1. Gluconeogenesis increased from 0.29 to 0.59 (Gln) and 0.44 to
1.06 (Ala), while ammoniagenesis rose from 2.19 to 3.24 (Gln) and 1.54 to
2.56 (Ala) mumol X min-1 X g-1. In contrast, Lac uptake (2.71 mumol X min-1
X g-1) and gluconeogenesis from Lac (1.05 mumol X min-1 X g-1), which
equalled or exceeded the values observed with Gln or Ala in normal rats,
were unchanged by acidosis. These data suggest 1) that acidosis increases
gluconeogenesis from Gln and Ala by accelerating the glutamate deamination
process, and 2) that the glutamate originating from glutamine and alanine
are segregated in two different pools within the mitochondria with
different access to glutamate dehydrogenase activity. Net cellular uptake
of Gln was greater in acidotic chicken tubules, establishing an
intracellular concentration of 4.5 in acidotic vs. 3.0 mM in normal
chickens when 1 mM Gln was used in the incubation medium. In contrast, 1 mM
alanine uptake was not modified by acidosis, greater intracellular
metabolism lowering the cellular concentration of this amino acid. These
observations suggest that the cellular transport of glutamine but not that
of alanine is increased in tubular fragments of acidotic chickens.
