DIETARY EXCESS OF VITAMIN-B-6 AFFECTS THE CONCENTRATIONS OF AMINO-ACIDS IN THE CAUDATE-NUCLEUS AND SERUM AND THE BINDING-PROPERTIES OF SEROTONIN RECEPTORS IN THE BRAIN CORTEX OF RATS
Mc. Schaeffer et al., DIETARY EXCESS OF VITAMIN-B-6 AFFECTS THE CONCENTRATIONS OF AMINO-ACIDS IN THE CAUDATE-NUCLEUS AND SERUM AND THE BINDING-PROPERTIES OF SEROTONIN RECEPTORS IN THE BRAIN CORTEX OF RATS, The Journal of nutrition, 128(10), 1998, pp. 1829-1835
Vitamin B-6 is a cofactor in many reactions of nitrogen metabolism. De
ficiency alters tissue amino acid concentrations but effects of excess
vitamin B-6 have not been well described. We fed female rats (218 g,
7 per group) 1 (control), 10, 100, 175 or 250x) the National Research
Council recommended level of pyridoxine HCl (7 mg/kg) for 10 wk and me
asured serum amino acids, amino acids and neurotransmitters in brain r
egions and the binding properties of serotonin receptors in the cerebr
al cortex using a ketanserin binding assay. Rats were decapitated, and
unheparinized blood was obtained. In the caudate nucleus, concentrati
ons of glutamate, threonine, taurine, methionine, gamma-amino-butyric
acid and the sum of the essential amino acids in groups 10X and 100X w
ere similar to 130 to 180% of control levels (P < 0.05); groups 1X, 17
5X and 250X were not different. A similar pattern was seen in the seru
m for serine, glycine, aspartate and ornithine; the tatter two amino a
cids increased to over 200% of control in group 100X. In the ketanseri
n binding assay, both the antagonist binding affinity and the maximal
number of binding sites were higher for group 100X than for 1X, 175X a
nd 250X, and were higher for 10X than for 1X, Norepinephrine in the ra
phe nucleus followed a similar biphasic pattern. Excess dietary pyrido
xine affected brain and serum concentrations of some amino acids and b
inding properties of cortical serotonin receptors in a biphasic patter
n over the range of concentrations fed in this study.