Carbaryl-induced changes in indoleamine synthesis in the pineal gland and its effects on nighttime serum melatonin concentrations.
The effects of different doses of chronically administered carbaryl on rat pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity and pineal and serum melatonin levels during darkness (2300 h and 0100 h) when pineal melatonin synthesis is high were studied. Additionally, pineal levels of 5-hydroxytryptophan (5-HTP), serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) were estimated. Carbaryl was administered at total doses (over 6 days) of either 50, 125 or 250 mg/kg by gastric gavage. Control rats received vehicle (corn oil) only. During the study, the rats were exposed to light/dark cycles of 14:10 with lights off at 2100 h. Pineal NAT and HIOMT activities and pineal melatonin were increased at 0100 h following carbaryl administration at all three doses. Conversely, serum melatonin was increased at 2300 h after the 250 mg/kg dose of carbaryl while all three doses of the pesticide reduced serum melatonin levels at 0100 h. Pineal 5-HTP, 5-HT and 5-HIAA levels were usually increased at 2300 h but unaffected at 0100 h. The results indicate that carbaryl has significant effects on pineal melatonin synthesis and secretion.
Attia
A M
AM
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
Reiter
R J
RJ
Nonaka
K O
KO
Mostafa
M H
MH
Soliman
S A
SA
el-Sebae
A H
AH
D006916:5-Hydroxytryptophan / Q000096:biosynthesis; D000121:Acetylserotonin O-Methyltransferase / Q000187:drug effects; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D012721:Carbaryl / Q000633:toxicity*; D002940:Circadian Rhythm; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D010870:Pineal Gland / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051381:Rats; D012701:Serotonin / Q000096:biosynthesis
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D006916:5-Hydroxytryptophan; D000121:Acetylserotonin O-Methyltransferase; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin; D012721:Carbaryl