Melatonin and its analogs potentiate the nifedipine-sensitive high-voltage-activated calcium current in the chick embryonic heart cells.
Effects of melatonin and its analogs on the voltage-activated calcium current of embryonic chick ventricular cardiomyocytes were investigated. Myocytes were dissociated from 14- to 16-day-old chicks (yellow Red Rob) embryonic hearts and cultured for 2 3 days. Calcium currents were studied by the patch-clamp technique. Whole-cell current recording showed nifedipine-sensitive, high-voltage-activated L-type calcium current inactivated in 70-100 ms during the voltage step period of 200 ms. There was no evidence of low-voltage-activated T-type calcium channels. Melatonin (ejected solution: 50 micromol/L melatonin; concentration at the vicinity of recording cell: about 1-5 micromol/L melatonin) and its analogs, 2-iodomelatonin and 2-iodo-n-butanol-5-methoxytryptamine, significantly increased the amplitude of the calcium current by 42-62%. The effect of melatonin on the L-type calcium current was not desensitised by repeated melatonin treatment. Our results suggest a specific melatonin receptor-mediated action on the calcium channel of the embryonic chick myocyte. The melatonin-induced increase in high-voltage calcium current may increase myocyte contractility and enhance cardiac output. A regulatory role of melatonin on the chick cardiac function should be further considered.
Mei
Y A
YA
Department of Physiology and Biophysics, School of Life Science, Fudan University, Shanghai, China. yamei@fudan.edu.cn
Lee
P P
PP
Wei
H
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Zhang
Z H
ZH
Pang
S F
SF
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D004357:Drug Synergism; D008550:Melatonin / Q000031:analogs & derivatives / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011956:Receptors, Cell Surface / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D044094:Receptors, Melatonin
D000975:Antioxidants; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D009543:Nifedipine; D008550:Melatonin; D002118:Calcium