Myosin heavy chain mrnas transform to faster isoforms in
immobilized skeletal muscle: a quantitative pcr study.
J[umlaut]ank[umlaut]al[umlaut]a, Heidi, Veli-Pekka Harjola, Niels Erik
Petersen, and Matti H[umlaut]ark[diaeresis]onen.
Department of Clinical Chemistry, University of Helsinki,
Haartmaninkatu 4, SF-00290 Helsinki, Finland
APStracts 3:0559A, 1996.
A quantitative PCR method was used to measure the quantities of type
I, IIa, IIx and IIb myosin heavy chain (MHC) mRNAs in total RNA
preparations of the soleus, gastrocnemius and plantaris muscles of
normal and hindlimb immobilized rats. Type IIx and even type IIb MHC
mRNAs were demonstrated at extremely low levels in normal soleus,
2.1+/-0.4 x 105 and 5.0+/-0.2 x 105 molecules of mRNA per [mu]g total
RNA, respectively. Immobilization for one week significantly altered
the gene expression of MHC isoforms. In soleus both type IIx and IIb
MHC genes became significantly up-regulated, 24-fold (P<0.005)
and 1.6-fold (P<0.05), respectively. In gastrocnemius the
level of type IIa MHC mRNA decreased by 51% (P<0.01) and that
of type IIx MHC mRNA increased by 140% (P<0.05). In plantaris
the level of type IIa MHC mRNA decreased by 58% (P<0.005). In
conclusion, immobilization changed the MHC mRNA profile in three
different types of skeletal muscle towards faster isoforms. The
quantitative results permit evaluation of changes in mRNA levels
reliably.
Received 24 July 1996; accepted in final form 4 November 1996.
APS Manuscript Number A704-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996