title: Direct measurement of Ca2+ concentration in the SR of living cardiac myocytes.
abstract: Although abnormal sarcoplasmic reticulum (SR) Ca(2+) handling may cause heart failure, there has been no method to directly measure Ca(2+) concentration in SR ([Ca(2+)](SR)) of living cardiomyocytes. We have measured [Ca(2+)](SR) by expressing novel fluorescent Ca(2+) indicators yellow cameleon (YC) 2.1, YC3er, and YC4er in cultured neonatal rat cardiomyocytes. The distribution of YC2.1 was uniform in the cytoplasm, while that of YC3er/YC4er, containing the signal sequence which recruits them to SR, showed reticular pattern and was co-localized with SERCA2a. The treatment with caffeine reversibly decreased the emission ratio (R) in YC3er/YC4er-expressing myocytes, and the treatment with ryanodine and thapsigargin decreased R irreversibly. During the contraction-relaxation cycle, R was changed periodically in the YC2.1- and YC3er-expressing myocytes, but its direction of the change was opposite. These results suggest that YC3er/YC4er were specifically localized and functioned in SR as a [Ca(2+)](SR) indicator. This technique would be useful to understand the function of SR in failing myocardium.
authors.affiliation: Department of Cardiovascular Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kasai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yao
authors.forename: Tomomi
authors.initials: T
authors.lastname: Oyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akazawa
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Toko
authors.forename: Toshio
authors.initials: T
authors.lastname: Nagai
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kinugawa
authors.forename: Osami
authors.initials: O
authors.lastname: Kohmoto
authors.forename: Kei
authors.initials: K
authors.lastname: Maruyama
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Ryozo
authors.initials: R
authors.lastname: Nagai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyawaki
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D007150:Immunohistochemistry; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
chemical_list: D002118:Calcium