title: [Investigation of nuclear Ca2+ regulation in the isolated cardiac nuclei].
abstract: 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.
authors.affiliation: Department of Cardiology, Xinqiao hospital, Department of Pathophysiology, Third Medical University, Chongqing 400037.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.forename: Pei Yong
authors.initials: PY
authors.lastname: Wang
authors.forename: Zuo Yun
authors.initials: ZY
authors.lastname: He
mesh_terms: 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
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D000252:Calcium-Transporting ATPases; D002118:Calcium