Details

Autor(en) / Beteiligte

• Criswell, David S
• Hodgson, Vanessa R. M
• Hardeman, Edna C
• Booth, Frank W

Titel

Nerve-responsive troponin I slow promoter does not respond to unloading

Ist Teil von

• Journal of applied physiology (1985), 1998-03, Vol.84 (3), p.1083-1087

Ort / Verlag

Legacy CDMS: Am Physiological Soc

Erscheinungsjahr

1998

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• 1  Department of Integrative Biology, Pharmacology, and Physiology, University of Texas Medical School, Houston, Texas 77030; and 2  Muscle Development Unit, The Children's Medical Research Institute, Wentworthville, New South Wales 2145, Australia We examined the regulation of the troponin I slow (TnIs) promoter during skeletal muscle unloading-induced protein isoform transition, by using a transgenic mouse line harboring the 4,200 to +12 base pairs region of the human TnIs promoter. Eighteen female transgenic mice (~30 g body mass) were randomly divided into two groups: weight-bearing (WB) controls ( n  = 9) and hindlimb unloaded (HU; n  = 9). The HU mice were tail suspended for 7 days. Body mass was unchanged in the WB group but was reduced ( 6%; P  < 0.05) after the HU treatment. Absolute soleus muscle mass ( 25%) and soleus mass relative to body mass ( 16%) were both lower ( P  < 0.05) in the HU group compared with the WB mice. Northern blot analyses indicate that 7 days of HU result in a 64% decrease ( P  < 0.05) in the abundance of endogenous TnIs mRNA (µg/mg muscle) in the mouse soleus. Furthermore, there is a trend for the abundance of the fast troponin I mRNA to be increased (+34%). Analysis of transgenic chloramphenicol acetyltransferase activity in the soleus muscle revealed no difference ( P  > 0.05) between WB and HU groups. We conclude that additional elements are necessary for the TnIs gene to respond to an unloading-induced, slow-to-fast isoform transition stimulus. transgenic mice; skeletal muscle; hindlimb unloading JAP 84(3):1083-1087 0161-7567/98 $5.00 Copyright © 1998 the American Physiological Society