Rostrocaudal variation of fiber type composition in rat intercostal muscles.
We used the histochemical stain for ATPase to compare the fiber-type composition of rat internal and external intercostal muscles from thoracic (T) segments 2-5, 8, and 11. At each level, type II fibers were more numerous than type I fibers, type II B fibers were more numerous than II A fibers, and type I fibers were more numerous in external than in internal intercostals. However, fiber type composition varied from segment to segment. For example, the proportion of type II A fibers increased in a rostrocaudal gradient in internal but not external intercostals, and type I fibers were more prevalent at rostral and caudal than at intermediate levels in both internal and external intercostals. These results provide a basis for interpreting previous physiological and molecular studies which have compared intercostal muscles from different segmental levels.
Cunningham
J M
JM
Department of Anatomy and Neurobiology, Washington University Medical Center, St. Louis, MO 63110.
Kaiser
K K
KK
Sanes
J R
JR
D000251:Adenosine Triphosphatases / Q000032:analysis*; D000818:Animals; D006651:Histocytochemistry; D006863:Hydrogen-Ion Concentration; D007366:Intercostal Muscles / Q000166:cytology / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D000251:Adenosine Triphosphatases