Acute effects of L-tryptophan on tryptophan hydroxylation rate in brain regions (hypothalamus and medulla) of rainbow trout (Oncorhynchus mykiss).
Levels of 5-hydroxytryptophan (5-HTP) in brain regions (hypopthalamus and medulla) of rainbow trout were analysed by HPLC-EC 0, 10, 30, and 40 min after intraperitoneal administration of different doses of L-tryptophan (Trp) (0, 12.5, and 25 mg. kg(-1) body weight) in fish treated with 3-hydroxybenzylhydrazine (NSD1015; 75 mg. kg(-1)). The results show that, in control fish, 5-HTP levels in hypothalamus (58.03 +/- 6.36 pg. mg(-1) brain tissue) were significantly higher than those observed in medulla (28.04 +/- 4.32 pg. mg(-1) brain tissue). Basal tryptophan hydroxylation rates (after 0 mg. kg(-1) Trp administration) were 0.42 +/- 0.07 pg 5-HTP. mg(-1). min(-1), and 0.63 +/- 0.24 pg 5HTP. mg(-1). min(-1), for hypothalamus and medulla respectively. On the other hand, the results demonstrate that L-tryptophan administration induced significant increases in the rate of tryptophan hydroxylation, both in hypothalamus and medulla. These findings indicate that, in a way similar to that observed in mammals, brain tryptophan hydroxylase is unsaturated by its substrate (tryptophan) under normal physiological conditions. J. Exp. Zool. 286:131-135, 2000.
Aldegunde
M
M
Laboratorio de Fisioloxía Animal (Departamento de Fisioloxía), Facultade de Bioloxía, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Spain. fsaldegu@uscmail.usc.es
Soengas
J L
JL
rozas
G
G
D006916:5-Hydroxytryptophan / Q000378:metabolism; D000818:Animals; D007031:Hypothalamus / Q000201:enzymology*; D008526:Medulla Oblongata / Q000201:enzymology*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012701:Serotonin / Q000096:biosynthesis; D014364:Tryptophan / Q000494:pharmacology*; D014365:Tryptophan Hydroxylase / Q000378:metabolism*
D012701:Serotonin; D014364:Tryptophan; D006916:5-Hydroxytryptophan; D014365:Tryptophan Hydroxylase