In vivo and in vitro effects of the pineal gland and melatonin on [Ca(2+) + Mg2+]-dependent ATPase in cardiac sarcolemma.
The possible diurnal variation in cardiac [Ca(2+) + 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 sarcolemmal membrane [Ca(2+) + 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 [Ca(2+) + 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 [Ca(2+) + 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 [Ca(2+) + 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.
Chen
L D
LD
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
Tan
D X
DX
Reiter
R J
RJ
Yaga
K
K
Poeggeler
B
B
Kumar
P
P
Manchester
L C
LC
Chambers
J P
JP
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D003623:Dark Adaptation; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology / Q000502:physiology*; D009206:Myocardium / Q000201:enzymology*; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000187:drug effects / Q000201:enzymology*
D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D008550:Melatonin