Implication of tryptophan in the stimulatory effect of delta-sleep-inducing peptide on indole secretion from perifused rat pineal glands.
We have recently demonstrated that delta-sleep-inducing peptide (DSIP) stimulates indolamine secretion from rat pineal glands. In the present study, we show that tryptophan (TRP), as well as DSIP, stimulate melatonin (MEL) and 5-methoxy-tryptophol (5-ML) secretion in a dose-dependent manner between 5 x 10(-6) and 10(-4) M. The kinetic characteristics of the MEL and 5-ML secretion and the response induced by the two substances were similar. The increase in MEL secretion in response to 10(-4) M DSIP was completely inhibited by pretreatment of the pineals with 10(-5) M phenanthroline (amino-peptidase inhibitor), suggesting that stimulatory effect of DSIP was due to TRP liberated by peptide degradation. This mechanism occurring in the pineal was confirmed using 10(-4) M para-chlorophenylalamine (TRP hydroxylase inhibitor), which reduced the pineal response to 10(-4) and 10(-5) M DSIP by 50 and 100%, respectively.
Ouichou
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URA-CNRS 1332 Neurobiologie des fonctions rythmiques et saisonnières, Université Louis Pasteur, Strasbourg, France.
Pévet
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D000595:Amino Acid Sequence; D000818:Animals; D003701:Delta Sleep-Inducing Peptide / Q000737:chemistry / Q000494:pharmacology*; D010134:Fenclonine / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008969:Molecular Sequence Data; D010477:Perfusion; D010618:Phenanthrolines / Q000494:pharmacology; D010870:Pineal Gland / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014364:Tryptophan / Q000378:metabolism / Q000494:pharmacology*
D007211:Indoles; D010618:Phenanthrolines; D003701:Delta Sleep-Inducing Peptide; C002465:methoxytryptophol; D014364:Tryptophan; D008550:Melatonin; D010134:Fenclonine