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.
Department of Medicine, Oregon Health Sciences University, Portland.
M
M
Murakami
M A
MA
Greer
S E
SE
Greer
S
S
Hjulstad
K
K
Tanaka
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