Open AccessIndividual, age and sex differences in fiber type composition of slow and fast muscles of adult Lewis rats: comparison with other rat strains
Author(s) -
Petr Novák,
Gisela Zachařová,
Tomáš Soukup
Publication year - 2010
Publication title -
physiological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.647
H-Index - 70
eISSN - 1802-9973
pISSN - 0862-8408
DOI - 10.33549/physiolres.931827
Subject(s) - fiber type , soleus muscle , muscle fibre , significant difference , age groups , composition (language) , chemistry , medicine , fiber , endocrinology , anatomy , biology , skeletal muscle , linguistics , philosophy , demography , organic chemistry , sociology
We analyzed fiber type composition of soleus and extensordigitorum longus (EDL) muscles of 3- to 19-month-old male andfemale inbred Lewis rats using histochemical demonstration ofmATPase activity. The rats were divided into four groups of themean age of 3, 6, 9 and 14 months. We found that the soleusmuscle of 3-month-old rats contained significantly more of fast2A fibers and less of slow type 1 fibers compared to older rats,while no significant difference was found between female andmale rats at any age group. In contrast, we found no significantdifference in the EDL fiber type composition among the agegroups, but we found that the EDL muscle of female ratscontained significantly less 2A fibers and more 2B fibers than thatof male animals. Our results thus revealed an age difference inthe soleus muscle and a sex difference in the EDL muscle amongpostnatal Lewis rats. The number of slow type 1 fibers in thesoleus muscle varied between 87 and 100 % and that of 2Afibers between 13 and 0 %. In the EDL the percentage of type 1fibers varied between 2.6 and 8.7 %, that of 2A fibers between12.6 and 25.8 % and that of 2B fibers between 70.4 and 81.6 %.Both muscles thus exhibited a considerable degree of variabilityamong individual animals even in the same age group.Furthermore, a comparison of the Lewis rats with literature dataof other rat strains showed that the number of fast 2A fibers inthe soleus muscle of 4-month-old and older animals decreased inthis order: SHR > Lister Hooded > Fisher 344 > SpragueDawley > Wistar > WBN/Kob > Lewis strain, being almost 20 % in the SHR and less than 2 % in the Lewis rats. In contrast, the “fastest” composition (judged according to the percentage of thefastest 2B fibers) of the EDL muscle was demonstrated by Lewis,Wistar and Fisher 344 rats (about 75 %), while Sprague-Dawleyand WBN/Kob rats contained only about 50 % of 2B fibers. Thepercentage of slow type 1 fibers in the EDL was low in all strains(about 5 %). Our results thus show that the individual, age andsex as well as inter-strain differences in muscle fiber typecomposition should not be ignored when comparing results ofdifferent studies. We also demonstrated that the inbred Lewisstrain appears to have more “specialized” muscle composition, asits soleus is the “slowest” and its EDL is the “fastest” among theroutinely used rat strains.