Ca2+ handling and myofibrillar Ca2+ sensitivity in ferret cardiac myocytes with pressure-overload hypertrophy.

Abstract

Experiments were performed in aequorin-loaded left ventricular myocytes isolated from hypertrophied hearts and age-matched controls. Five to six months after postvalvular aortic banding, left ventricular hypertrophy was present, as indicated by a 97% (P < 0.001) increase in the left ventricular weight-to-body weight ratio and a 24% (P < 0.001) increase in cell width. In comparison with controls, the hypertrophied myocytes demonstrated that 1) contraction duration was prolonged by 37% (P < 0.001) and was associated with a 44% (P < 0.001) prolongation of the intracellular Ca2+ transient; 2) peak systolic shortening was decreased by 31% (P < 0.001) and was associated with a 21% (P < 0.001) decrease in peak systolic intracellular Ca2+ concentration; 3) both the peak systolic intracellular Ca2+ concentration-to-peak shortening relationship and the intracellular Ca2+ concentration-to-cell shortening relationship at the time of the peak twitch were shifted downward, suggesting a decrease in myofilament Ca2+ responsiveness; and 4) isoproterenol (5 x 10(-8) M) produced equal increases in the peak systolic intracellular Ca2+ of control and hypertrophied myocytes (88 vs. 90%; P > 0.05) in contrast to much smaller increases in the peak cell shortening (170 vs. 73%; P < 0.02) of the hypertrophied myocytes, suggesting a decrease in myofilament Ca2+ responsiveness. These data demonstrate that the hypertrophy-related abnormalities in intracellular Ca2+ handling and mechanical function, previously reported in aequorin-loaded multicellular muscle preparations, are present in isolated myocytes, arguing against changes in the interstitium as essential causative factors.

• Authors: J Wang, K Flemal, Z Qiu, L Ablin, W Grossman, J P Morgan
• Journal: The American journal of physiology (Am J Physiol) Vol. 267 Issue 3 Pt 2 Pg. H918-24 (Sep 1994) ISSN: 0002-9513 [Print] United States
• PMID: 8092296 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Aequorin
• Calcium

Topics

• Aequorin
• Animals
• Calcium (metabolism, physiology)
• Cardiomegaly (etiology, metabolism, physiopathology)
• Cell Separation
• Ferrets
• Hypertension (complications)
• Intracellular Membranes (metabolism)
• Male
• Myocardial Contraction
• Myocardium (metabolism, pathology)
• Myofibrils (physiology)