Circadian rhythm in pineal tyrosine hydroxylase.
Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine synthesis. The rat pineal gland is richly innervated by sympathetic nerves from the superior cervical ganglia. The activity of tyrosine hydroxylase was measured in rat pineal gland at 4-hour intervals over a daily cycle of 12 hours of light (7 a.m. to 7 p.m.) and 12 hours of darkness. The results indicate a circadian rhythm with the maximum activity, at 11 p.m. to 3 a.m., about triple the low values observed at 3 p.m. The pattern is similar in phase to that previously reported for melatonin and hydroxyindole-O-methyl transferase activity.
D000818:Animals; D002940:Circadian Rhythm; D066298:In Vitro Techniques; D006899:Mixed Function Oxygenases; D010870:Pineal Gland / Q000201:enzymology*; D051381:Rats
D006899:Mixed Function Oxygenases