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.
Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284-7762.
L D
LD
Chen
D X
DX
Tan
R J
RJ
Reiter
K
K
Yaga
B
B
Poeggeler
P
P
Kumar
L C
LC
Manchester
J P
JP
Chambers
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