Tryptophan administration in rats enhances phagocytic function and reduces oxidative metabolism.
OBJECTIVE
Since the tryptophan-derived metabolites serotonin and melatonin have been shown to possess reinforcing and/or antioxidant properties in the immune system, this investigation was aimed at determining the possible effect of a 7-day administration of tryptophan (125 mg/kg b.w.), the precursor of both the neurotransmitter and the indole, on the phagocytosis and free radical scavenging of peritoneal macrophages from adult male Wistar rats.


METHODS
Phagocytosis was measured by the latex-bead phagocytosis index (PI), i.e., the number of latex beads ingested by 100 macrophages, the phagocytosis percentage (PP), i.e., the percentage of cells that had phagocytosed at least one latex bead, and the phagocytosis efficiency (PE), i.e., the ratio PI:PP which indicates how effectively the phagocytes ingested the particles. Oxidative metabolism was measured by the nitroblue tetrazolium (NBT) reduction test.


RESULTS
In control conditions, PI, PP, and PE significantly increased during the dark period, while the superoxide anion levels underwent a significant reduction. Tryptophan treatment significantly raised the phagocytosis parameters in a general fashion, as well as decreasing the oxidative metabolism with respect to the control values. Also, there was a significant rise in the MESORs of the PI and PE (of around 16% and 12%, respectively), the MESOR of the percentage of NBT reduction was significantly reduced (19%).


CONCLUSIONS
Orally administered tryptophan enhanced the phagocytic response and detoxification of superoxide anion radicals derived from this immune function in the peritoneal macrophages of rats, very probably through its conversion to the immunoregulatory molecules, serotonin and melatonin.
Sanchez
Soledad
S
Department of Physiology, Faculty of Science, University of Extremadura, Badajoz, Spain. solsan@unex.es
Paredes
Sergio D
SD
Sanchez
Cristina L
CL
Barriga
Carmen
C
Reiter
Russel J
RJ
Rodriguez
Ana B
AB
D000704:Analysis of Variance; D000818:Animals; D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013481:Superoxides / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism* / Q000494:pharmacology
D000975:Antioxidants; D016166:Free Radical Scavengers; D013481:Superoxides; D014364:Tryptophan