Aging-dependent depression in the kinetics of force development in rat skinned myocardium

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 276; no. 5; pp. H1511 - H1519
• Main Authors: Fitzsimons, Daniel P, Patel, Jitandrakumar R, Moss, Richard L
• Format: Journal Article
• Language: English
• Published: United States 01.05.1999
• Subjects: Acetates - pharmacology; Aging - physiology; Animals; Calcium Chloride - pharmacology; Chelating Agents - pharmacology; Contractile Proteins - analysis; Ethylenediamines - pharmacology; Heart Ventricles - chemistry; Heart Ventricles - cytology; Kinetics; Male; Muscle Fibers, Skeletal - drug effects; Muscle Fibers, Skeletal - physiology; Myocardial Contraction - drug effects; Myocardial Contraction - physiology; Myocardium - chemistry; Myocardium - cytology; Myocardium - metabolism; Myosin Heavy Chains - metabolism; Organ Culture Techniques; Organ Size; Photochemistry; Rats; Rats, Inbred F344; Ventricular Function
• ISSN: 0363-6135; 0002-9513; 1522-1539
• DOI: 10.1152/ajpheart.1999.276.5.h1511

Department of Physiology, University of Wisconsin School of Medicine, Madison, Wisconsin 53706 Normal aging of the rodent heart results in prominent prolongation of the twitch. We tested the hypothesis that increased expression of -myosin heavy chain (MHC), as occurs in the normal aging process in the rodent heart, contributes to the prolongation of the twitch by depressing the kinetics of cross-bridge interaction. Using 3-, 9-, 21-, and 33-mo-old male Fischer 344 × Brown Norway F 1 hybrid rats, we examined both the rate of tension development ( k Ca ) and unloaded shortening velocity in chemically skinned myocardium. Although k Ca in all four age groups was dependent on the level of Ca 2+ activation, both submaximal and maximal k Ca were significantly slower in 9-, 21-, and 33-mo-old rats relative to 3-mo-old rats. Furthermore, unloaded shortening velocity was significantly reduced in 9-, 21-, and 33-mo-old rats compared with 3-mo-old rats. Collectively, these data strongly suggest that the aging-related increase in -MHC expression results in a progressive slowing of cross-bridge interaction kinetics in skinned myocardium, which most likely contributes to the overall aging-dependent reduction in myocardial functional capacity. myosin heavy chain; caged calcium; cross-bridge kinetics; Fischer 344 × Brown Norway rats