Utilization of alanine for glucose formation in isolated rabbit kidney-cortex tubules.
In kidney cortex tubules isolated from fed rabbits L-alanine is not utilized as glucose precursor, when added as a sole substrate. However, this amino acid decreases gluconeogenesis from low (up to 1 mM) 2-oxoglutarate concentrations and stimulates this process at higher (2.5-10 mM) ketoacid contents in the suspension medium. Aminooxyacetate, an inhibitor of aminotransferases, abolishes both inhibitory and stimulatory effects of L-alanine on glucose formation. The addition of 2-oxoglutarate increases the incorporation of L-[U-14C]alanine to glucose from 8- to 123-fold, depending upon the ketoacid and alanine concentrations used. In contrast, nonlabelled L-alanine decreases the incorporation of low [U-14C)2-oxoglutarate concentrations into glucose, while it does not affect contribution of 5 mM ketoacid to gluconeogenesis. The data indicate that (i) in the presence of 2-oxoglutarate L-alanine is utilized as glucose precursor in rabbit renal tubules and (ii) this amino acid may decrease the contribution of low extracellular concentrations of the ketoacid to gluconeogenesis.
Zabłocki
K
K
Institute of Biochemistry, University of Warsaw, Poland.
Bryła
J
J
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D005943:Gluconeogenesis; D005947:Glucose / Q000096:biosynthesis*; D066298:In Vitro Techniques; D007656:Ketoglutaric Acids / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D008297:Male; D011817:Rabbits
D007656:Ketoglutaric Acids; D005947:Glucose; D000409:Alanine