Publication: Quantification of daily melatonin synthesis in the hamster pineal gland
Issued Date
1980-01-01
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ISSN
19457170
00137227
00137227
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2-s2.0-0018914588
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Mahidol University
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SCOPUS
Bibliographic Citation
Endocrinology. Vol.106, No.1 (1980), 231-236
Suggested Citation
Mark D. Rollag, Elizabeth S. Panke, Wantanee Trakulrungsi, Chatchai Trakulrungsi, Russel J. Reiter Quantification of daily melatonin synthesis in the hamster pineal gland. Endocrinology. Vol.106, No.1 (1980), 231-236. doi:10.1210/endo-106-1-231 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/11086
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Title
Quantification of daily melatonin synthesis in the hamster pineal gland
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Abstract
The rate of melatonin synthesis within pineal glands of female hamsters maintained in an 8-h light, 16-h dark photoperiod has been calculated. When exposed to these photoperiodic conditions, female hamsters exhibited a distinct circadian rhythm in pineal melatonin content, with basal concentrations of 40-90 pg/gland found throughout the day and during the first 10 h of darkness and a peak concentration of 847 pg/ gland found near the end of the dark phase 1 h before lights on. The rates of melatonin synthesis required to produce this concentration profile ranged from 1.6 pg/min during the daylight hours to a maximum of 70.6 pg/min 14 h after the onset of darkness. The total quantity of melatonin synthesized throughout the 24-h cycle was calculated to be 18.6 ng. Exposure of hamsters to an unexpected source of white light at the time of the nocturnal peak in pineal melatonin content resulted in a rapid decay in pineal melatonin concentrations. The rate constant obtained (−0.0788 min −1 ) corresponded to a t 1/2 of approximately 9 min. Exposure of rats to a similar experimental paradigm resulted in a 6 min t 1/2 for pineal melatonin content and a 4 min t 1/2 for pineal N-acetylserotonin transferase activity. The quantity of exogenously administered melatonin required to induce vaginal acyclicity in female hamsters when injected sc 0.5 h before lights out in a 14-h light, 10-h dark photoperiod was determined. Dosages of 1.6-12.8 μg melatonin/day induced acyclicity in 50% of the female hamsters within 40-52 days. Dosages less than 1.6 μg/day did not interrupt vaginal cyclicity. Hamsters exposed to an 8-h light, 16-h dark photoperiod required 104 days of exposure before acyclicity was found in 50% of the population. At the end of 105 days of treatment, mean uterine weights averaged between 133 ± 24 and 215 ± 33 mg/100 g BW (mean ± sem) in hamsters treated with dosages greater than 1.6 μg melatonin/day and between 311 ± 35 and 369 ± 6 mg/100 g BW in hamsters treated with dosages less than 1.6 μg/day. Hamsters receiving diluent had mean uterine weights of 363 ± 15 mg/100 g BW. Those exposed to an 8-h light, 16-h dark photoperiod had mean uterine weights of 252 ± 22 mg/100 g BW. © 1980 by The Endocrine Society.