Comparison of the nocturnal temporal profiles of N-acetyl-transferase and thyroxine 5'-deiodinase in rat pineal.
The nocturnal temporal patterns of pineal N-acetyltransferase (NAT) and type II thyroxine 5'-deiodinase (5'-D) were compared in the same animals. Both NAT and 5'-D had a similar rise to a midnight zenith with the same lag period but 5'-D rose to its peak 1 h before NAT. The temporal profiles of decrease in enzyme activities were quite different, with 5'-D declining long before NAT. Acute light exposure caused a rapid dramatic decrease in NAT but not in 5'-D. These data suggest that different mechanisms are in involved in the decrease of these two enzyme activities. The role of the antecedent rise in 5'-D activity in the nocturnal rise of NAT activity is apparently minor at most, since pretreatment with iopanoic acid completely blocked the nocturnal rise in 5'-D but had no effect on the nocturnal rise in NAT nor on the acute fall in NAT from its midnight zenith after exposure to light.
Murakami
M
M
Department of Medicine, Oregon Health Sciences University, Portland.
Greer
M A
MA
Greer
S E
SE
Hjulstad
S
S
Tanaka
K
K
D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism; D000123:Acetyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007480:Iopanoic Acid / Q000494:pharmacology; D008027:Light; D008297:Male; D010870:Pineal Gland / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D007453:Iodide Peroxidase; D000121:Acetylserotonin O-Methyltransferase; D000123:Acetyltransferases; D007480:Iopanoic Acid