Myofibrillar calcium sensitivity of isometric tension is increased in human dilated cardiomyopathies: role of altered beta-adrenergically mediated protein …

MR Wolff, SH Buck, SW Stoker… - The Journal of …, 1996 - Am Soc Clin Investig
MR Wolff, SH Buck, SW Stoker, ML Greaser, RM Mentzer
The Journal of clinical investigation, 1996Am Soc Clin Investig
To examine the role of alterations in myofibrillar function in human dilated cardiomyopathies,
we determined isometric tension-calcium relations in permeabilized myocytesized
myofibrillar preparations (n= 16) obtained from left ventricular biopsies from nine patients
with dilated cardiomyopathy (DCM) during cardiac transplantation or left ventricular assist
device implantation. Similar preparations (n= 10) were obtained from six normal hearts used
for cardiac transplantation. Passive and maximal Ca2+-activated tensions were similar for …
To examine the role of alterations in myofibrillar function in human dilated cardiomyopathies, we determined isometric tension-calcium relations in permeabilized myocytesized myofibrillar preparations (n = 16) obtained from left ventricular biopsies from nine patients with dilated cardiomyopathy (DCM) during cardiac transplantation or left ventricular assist device implantation. Similar preparations (n = 10) were obtained from six normal hearts used for cardiac transplantation. Passive and maximal Ca2+-activated tensions were similar for the two groups. However, the calcium sensitivity of isometric tension was increased in DCM compared to nonfailing preparations ([Ca2+]50=2.46+/-0.49 microM vs 3.24+/-0.51 microM, P < 0.001). In vitro treatment with the catalytic subunit of protein kinase A (PKA) decreased calcium sensitivity of tension to a greater degree in failing than in normal preparations. Further, isometric tension-calcium relations in failing and normal myofibrillar preparations were similar after PKA treatment. These findings suggest that the increased calcium sensitivity of isometric tension in DCM may be due at least in part to a reduction of the beta-adrenergically mediated (PKA-dependent) phosphorylation of myofibrillar regulatory proteins such as troponin I and/or C-protein.
The Journal of Clinical Investigation