HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 93/3/399    most recent expphysiol.2007.040485v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mutungi, G. Search for Related Content PubMed PubMed Citation Articles by Mutungi, G.

¹ School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK

Although numerous studies have recently implicated the calcineurin–nuclear factor of activated T-cells (Cn–NFAT) signalling pathway in the regulation of activity-dependent fibre type switching in adult mammalian skeletal muscles, little is known about the endogenous expression of NFAT proteins in the various fibre types present in these muscles. In this study, the immunolocalization of NFATc1 (also known as NFATc or NFAT2) in the extensor digitorum longus (EDL; a mainly fast-twitch muscle) and the soleus (a predominantly slow-twitch muscle) muscles of adult (90-day-old) Wistar rats was investigated. The results show that NFATc1 is expressed only in oxidative fibres (i.e. type I and type IIA fibres) that stain intensely for succinate dehydrogenase activity irrespective of whether they are from the fast- or slow-twitch muscle. Thus, 99 ± 4% (n = 7 rats) of the muscle fibres in the soleus and 42 ± 2% (n = 7 rats) of those in the EDL expressed NFATc1. In the soleus muscle fibres, NFATc1 was localized mainly in the fibre nuclei, whereas in the EDL fibres it was localized in both the cytoplasm and the nuclei. However, no difference in its localization was observed between type I and type IIA fibres in both muscles. Western blot experiments showed that the soleus expressed more NFATc1 proteins than the EDL. From these results, we suggest that NFATc1 controls the number and distribution of both type I and type IIA fibres, as well as the oxidative capacity of adult mammalian skeletal muscles.

(Received 28 August 2007; accepted after revision 25 October 2007; first published online 26 October 2007)
Corresponding author G. Mutungi: School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK. Email: g.mutungi{at}uea.ac.uk