Parathion (O,O-dimethyl-O-p-nitrophenyl phosphorothioate) induces pineal melatonin synthesis at night.
The effects of parathion on male rat pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity and pineal and serum melatonin levels at the end of light period (2000 h) and at night (2300 h and 0100 h) were studied. Additionally, pineal levels of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) were estimated. Parathion was administered intragastrically at total doses (over 6 days) of either 6.5 or 13 mg/kg. Control rats received vehicle (corn oil) only. During the study, the rats were exposed to light:dark cycles of 14:10 with light off at 2100 h. Pineal NAT activity was increased at 0100 h following parathion administration at both doses, but HIOMT activity was unaffected. Pineal and serum melatonin levels were increased at night (2300 h and 0100 h) after the 13 mg/kg dose of parathion while the lower dose increased pineal melatonin only at 0100 h. Also, both doses decreased 5-HTP at 2000 h while the lower dose increased it at 2300; 5-HT was significantly decreased at 2300 h and 5-HIAA levels were lower but only significantly so for the 13 mg/kg dose at 2000 h. The results indicate that parathion has significant effects on pineal melatonin synthesis by mechanisms which remain unknown.
Attia
A M
AM
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
Reiter
R J
RJ
Stokkan
K A
KA
Mostafa
M H
MH
Soliman
S A
SA
el-Sebae
A K
AK
D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism*; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D002940:Circadian Rhythm / Q000187:drug effects*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000096:biosynthesis* / Q000097:blood; D010278:Parathion / Q000494:pharmacology*; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D010278:Parathion; D000121:Acetylserotonin O-Methyltransferase; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin