[Investigation of nuclear Ca2+ regulation in the isolated cardiac nuclei].
To investigate the regulation of Ca2+ in the isolated cardiac nuclei from rats which may illuminated the mechanism of nuclear calcium transport system. Elocity and isopyknic gradient centrifugation were employed to fractionate rat cardiac nuclei. Then fluo-4 confocal microscopy techniques was used to verify the changes of nuclear Ca2+. There are calcium-dependent Ca2+ uptake in the cardiac nuclear obtained from normal rats. The accumulation Ca2+ of cardiac nuclei in vitro from the incubating medium were not consistent with free [Ca2+] in incubating medium. The nuclear envelope was initially loaded with Ca2+ (1 mmol/L ATP and approximately 100 nmol/L Ca2+), Adequate Ca2+ loading was next confirmed by imaging the nuclear envelope and nucleoplasm. Exposure of Ca2+ -loaded nuclei to IP3, ryanodine or ryanodine + thapsigargin, respectively, resulted in a rapid and transient elevation of nucleoplasmic Ca2+ free concentration, this effects were abolished by pretreatment of cardiac nuclei with Ca2+ -ATPase inhibitor thapsigargin. Thapsigargin and IP3 receptor antagonist heparin induced nucleoplasmic Ca2+ free concentration decrease. Fluorescence experiments indicated that both ryanodine receptors and Ca2+ -ATPase were distributed in the outer layer of nuclear envelope, and inositol 1,4,5-trisphosphate receptors mainly dispersively localized at inner layer of nuclear envelope. The present study demonstrates that nuclear calcium were regulated by free Ca2+, IP3 and ryanodine. The results suggested calcium transport system might be present in the myocardial nuclei, the myocardial nuclei might served as one of calcium pools in myocardial cell.
Liu
Jian
J
Department of Cardiology, Xinqiao hospital, Department of Pathophysiology, Third Medical University, Chongqing 400037.
Wang
Pei Yong
PY
He
Zuo Yun
ZY
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism
D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D000252:Calcium-Transporting ATPases; D002118:Calcium