In vivo and in vitro effects of the pineal gland and melatonin on [Ca2++ Mg2+]-dependent ATPase in cardiac sarcolemma |
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Authors: | Li-Dun Chen Dun-Xian Tan Russel J Reiter Ken Yaga Burkhard Poeggeler Pramod Kumar Lucien C Manchester James P Chambers |
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Institution: | Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX;Brain Research Laboratory of Biochemistry;The University of Texas at San Antonio, San Antonio, TX, U.S.A. |
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Abstract: | Abstract: The possible diurnal variation in cardiac Ca2++ Mg2+]-dependent ATPase (Ca2+ pump) activity and the influence of pinealectomy and melatonin on this enzyme in rat heart have been studied. Lowest levels of cardiac sarcolemma] membrane Ca2++ Mg2+]-dependent ATPase activity were measured in late afternoon in rats kept under a 14:10 light:dark cycle. Late in the dark phase the enzyme activity began to increase with the rise continuing until 0900, 3 hr after light onset. These time-dependent changes in Ca2++ Mg2+]-dependent ATPase activity did not occur in either pinealectomized or light-exposed rats suggesting that melatonin, secreted from the pineal gland during the night, induces the change in Ca2++ Mg2+]-dependent ATPase activity. In vitro studies in which cardiac tissue was incubated in the presence of melatonin over a wide range of doses showed that this indole stimulated the Ca2+ pump. The half-maximal effect of melatonin was observed at a melatonin concentration of 28 ng/ml. These findings suggest that the daily change in Ca2++ Mg2+]-dependent ATPase activity in the sarcolemma of heart tissue is a result of the circadian rhythm in pineal melatonin production and secretion. These findings may be applicable to normal cardiac physiology. |
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Keywords: | pineal gland melatonin [Ca2++ Mg2+]-dependent ATPase heart sarcolemma |
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