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.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of pineal research|
|State||Published - May 1993|
- [Ca+ Mg]‐dependent ATPase
- pineal gland
ASJC Scopus subject areas