Effects of dilated cardiomyopathy on the diaphragm in the Syrian hamster

Stassijns, G.; Gayan-Ramirez, G.; De Leyn, P.; de Bock, V.; Dom, R.; Lysens, R.; Decramer, M.

doi:10.1183/09031936.99.13239199

Title

Effects of dilated cardiomyopathy on the diaphragm in the Syrian hamster

Author

Stassijns, G.

Gayan-Ramirez, G.

De Leyn, P.

de Bock, V.

Dom, R.

Lysens, R.

Decramer, M.

Abstract

This study aimed to elucidate changes in respiratory muscles and their mechanism in cardiomyopathy. The contractile properties and histology of the diaphragm, as well as serum levels of insulin-like growth factor (IGF)-1, were examined in 10 hamsters with idiopathic dilated cardiomyopathy (CM) and 10 controls. At 28 weeks, body weight in CM was reduced compared with controls (114+/-10 versus 144+/-14 g, p<0.0001). The ratio of diaphragm to body weight was significantly higher in CM than in controls (0.228+/-0.015 versus 0.182+/-0.017, p<0.0001). In vitro, maximal diaphragmatic twitch (303+/-63 versus 455+/-119 g x cm(-2)) and tetanic tensions (1,555+/-369 versus 2,204+/-506 g x cm(-2)) were significantly lower in CM than in controls (p<0.005). The half-relaxation time was significantly shorter in CM (19+/-1 ms) than in controls (24+/-3 ms, p<0.0005). Fatiguability at 25 Hz was significantly less in CM (28%) than in controls (42%, p<0.0001). Diaphragm and gastrocnemius adenosine triphosphatase staining showed type I fibre atrophy in CM, associated with an increase in the number of type I fibres in the diaphragm. Histological examination of both muscles revealed an abnormal muscular pattern. Finally, serum levels of IGF-1 were 47% lower in the CM group than in controls (p<0.0001) and were clearly related to the changes in the contractile properties and histology of the diaphragm. In conclusion, cardiomyopathy in hamsters: 1) depressed the force-generating capacity and shortened the relaxation of the hamster diaphragm; 2) induced type I fibre atrophy in combination with a myopathic pattern; and 3) was associated with a significant reduction in serum levels of insulin-like growth factor-1, related to the diaphragmatic changes. Whether these changes are primary myopathic or secondary to heart failure remains to be elucidated.

Language

English

Source (journal)

The European respiratory journal / European Respiratory Society [Lausanne] - Copenhagen, 1988, currens

Publication

Copenhagen : 1999

ISSN

0903-1936 [print]

1399-3003 [online]

DOI

10.1183/09031936.99.13239199

Volume/pages