Pineal indoleamine metabolism in pyridoxine-deficient rats.
Pyridoxine deficiency causes physiologically significant decrease in brain serotonin (5-HT) due to decreased decarboxylation of 5-hydroxytryptophan (5-HTP). We have examined the effect of pyridoxine deficiency on indoleamine metabolism in the pineal gland, a tissue with high indoleamine turnover. Adult male Sprague-Dawley rats were fed either a pyridoxine-supplemented or pyridoxine-deficient diet for 8 weeks. Pyridoxine deficiency did not alter the pattern of circadian rhythm of pineal 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), N-acetylserotonin (NAS), and melatonin. However the levels of these compounds were significantly lower in the pineal glands of pyridoxine-deficient animals. Pineal 5-HTP levels were consistently higher in the pyridoxine-deficient animals and a conspicuous increase was noticed at 22.00 h. Increase in pineal NAS and melatonin levels caused by isoproterenol (5 mg/kg at 17.00 h) were significantly lower (P less than 0.05) in the pyridoxine-deficient animals. Treatment of pyridoxine-deficient rats with pyridoxine restored the levels of pineal 5-HT, 5-HIAA, NAS, and melatonin to values seen in pyridoxine-supplemented control animals. These results suggest that 5-HT availability could be an important factor in the regulation of the synthesis of pineal NAS and melatonin.
Viswanathan
M
M
Department of Biochemistry, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Siow
Y L
YL
Paulose
C S
CS
Dakshinamurti
K
K
D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D002940:Circadian Rhythm; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000031:analogs & derivatives* / Q000378:metabolism*; D026681:Vitamin B 6 Deficiency / Q000378:metabolism*
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D001142:Aromatic-L-Amino-Acid Decarboxylases; D008550:Melatonin; D007545:Isoproterenol; C006389:N-acetylserotonin