title: Magnitude of length-dependent changes in contractile properties varies with titin isoform in rat ventricles.
abstract: The effects of differential expression of titin isoforms on sarcomere length (SL)-dependent changes in passive force, maximum Ca(2+)-activated force, apparent cooperativity in activation of force (n(H)), Ca(2+) sensitivity of force (pCa(50)), and rate of force redevelopment (k(tr)) were investigated in rat cardiac muscle. Skinned right ventricular trabeculae were isolated from wild-type (WT) and mutant homozygote (Ho) hearts expressing predominantly a smaller N2B isoform (2,970 kDa) and a giant N2BA-G isoform (3,830 kDa), respectively. Stretching WT and Ho trabeculae from SL 2.0 to 2.35 μm increased passive force, maximum Ca(2+)-activated force, and pCa(50), and it decreased n(H) and k(tr). Compared with WT trabeculae, the magnitude of SL-dependent changes in passive force, maximum Ca(2+)-activated force, pCa(50), and n(H) was significantly smaller in Ho trabeculae. These results suggests that, at least in rat ventricle, the magnitude of SL-dependent changes in passive force, maximum Ca(2+)-activated force, pCa(50), n(H), and k(tr) is defined by the titin isoform.
authors.affiliation: Dept. of Physiology, Univ. of Wisconsin, 601 Science Drive, Madison, WI 53711, USA. patel@wisc.edu
authors.forename: Jitandrakumar R
authors.initials: JR
authors.lastname: Patel
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Pleitner
authors.forename: Richard L
authors.initials: RL
authors.lastname: Moss
authors.forename: Marion L
authors.initials: ML
authors.lastname: Greaser
mesh_terms: D000818:Animals; D001549:Benzamides; D002118:Calcium / Q000378:metabolism; D064211:Connectin; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D007536:Isomerism; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology; D009210:Myofibrils / Q000502:physiology; D010766:Phosphorylation / Q000502:physiology; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000502:physiology*; D013314:Stress, Mechanical; D013844:Thiazoles
chemical_list: C540332:4-(3-(hydroxyamino)-3-oxoprop-1-enyl)-N-(4-methyl-3-(4-(pyridin-3-yl)thiazol-2-ylamino)phenyl)benzamide; D001549:Benzamides; D064211:Connectin; D009124:Muscle Proteins; D013844:Thiazoles; C577295:Ttn protein, rat; D002118:Calcium