J. Albrecht et al., SYNAPTOSOMAL UPTAKE OF ALPHA-KETOGLUTARATE AND GLUTAMINE IN THIOACETAMIDE-INDUCED HEPATIC-ENCEPHALOPATHY IN RATS, Metabolic brain disease, 12(4), 1997, pp. 281-286
The kinetics of uptake of two astroglia-derived glutamate (GLU) precur
sors, alpha-ketoglutarate (alpha-KG) and glutamine (GLN) were determin
ed in synaptosomes derived from rats with acute hepatic encephalopathy
(HE) induced with a hepatotoxin, thioacetamide (TAA). TAA treatment i
ncreased by 33% Vmax for high affinity, low capacity alpha-KG uptake,
without influencing its Km. The increase of the uptake capacity for al
pha-KG may represent a response of the GLUergic nerve terminals to the
decreased cerebral alpha-KG content, which during HE is associated wi
th depressed activity of pyruvate carboxylase, an enzyme that replenis
hes alpha-KG in astrocytes. The result is thus consistent with the not
ion that HE affects the astroglial control of GLUergic neurotransmissi
on. The Km and Vmax for the low affinity, high capacity GLN uptake was
not affected by TAA treatment.