CHANGES IN MYOFIBRILLAR PROTEIN-COMPOSITION OF HUMAN DIAPHRAGM ELICITED BY CONGESTIVE-HEART-FAILURE

We describe the changes in proportions of myofibrillar proteins elicit ed by chronic congestive heart failure in the costal diaphragm (DIA) o f humans using one and two-dimensional electrophoretic techniques. Thr ee myosin heavy chain (MHC) isoforms were found in the DLA from contro l subjects: slow MHC I (43 +/- S.E. 2%), fast MHC IIa (41 +/- 2%) and fast MHC IIb (17 +/- 1%). In heart failure DIA, the percentage of MHC I was increased to 57 +/- 2%, while that of MHC IIb was decreased to 8 +/- 2 (P<0.001 for both cases). Similarly, this DIA had higher molar ratios (%) of the slow myosin light chain isoforms (i.e. 1sa, 1sb, and 2s), and lower molar ratios of the fast isoforms (i.e. 1f, 2f, and 3f ) than control DIA. Heart failure DIA also contained lower proportions of both alpha-tropomyosin and fast isoforms of troponin-T, I and C th an control DIA. These results indicate that heart failure elicits fast -to-slow transformations of both myosin and regulatory proteins of hum an costal DIA. These changes can be viewed as an increase in slow-twit ch characteristics of the DIA and differ from the adaptations elicited by heart failure in limb muscles. (C) 1996 Academic Press Limited