TY - JOUR
T1 - Histochemical and physiological characteristics of the rat diaphragm
AU - Metzger, J. M.
AU - Scheidt, K. B.
AU - Fitts, R. H.
PY - 1985
Y1 - 1985
N2 - The histochemical and contractile characteristics of the adult rat diaphragm were determined. Based on enzyme histochemistry, the rat diaphragm contained 40% type I, 27% type IIa, and 34% type IIb fibers. There were significantly more type I fibers in the ventral costal (VEN) compared with the crural (CRU) region of the muscle and a slightly higher percentage of type I's on the thoracic relative to the abdominal surface. The contractile properties and the effect of temperature (Q10) were similar in the VEN and CRU regions. Increasing temperature produced higher isometric peak tetanic tension, whereas twitch tension, contraction, and one-half relaxation time all decreased. The maximal shortening velocity increased linearly from 22 and 30°C, then plateaued before decreasing between 35 and 37°C. The VEN and CRU force-velocity curves became less concave as temperature increased from 22 to 35°C. Furthermore, the force-frequency relation of both regions was shifted to the right as temperature increased. The isometric and isotonic contractile properties and fiber type distribution are similar in the VEN and CRU regions of the diaphragm. The rat diaphragm is clearly heterogeneous in fiber type distribution and functionally lies intermediate between slow- and fast-twitch limb skeletal muscles.
AB - The histochemical and contractile characteristics of the adult rat diaphragm were determined. Based on enzyme histochemistry, the rat diaphragm contained 40% type I, 27% type IIa, and 34% type IIb fibers. There were significantly more type I fibers in the ventral costal (VEN) compared with the crural (CRU) region of the muscle and a slightly higher percentage of type I's on the thoracic relative to the abdominal surface. The contractile properties and the effect of temperature (Q10) were similar in the VEN and CRU regions. Increasing temperature produced higher isometric peak tetanic tension, whereas twitch tension, contraction, and one-half relaxation time all decreased. The maximal shortening velocity increased linearly from 22 and 30°C, then plateaued before decreasing between 35 and 37°C. The VEN and CRU force-velocity curves became less concave as temperature increased from 22 to 35°C. Furthermore, the force-frequency relation of both regions was shifted to the right as temperature increased. The isometric and isotonic contractile properties and fiber type distribution are similar in the VEN and CRU regions of the diaphragm. The rat diaphragm is clearly heterogeneous in fiber type distribution and functionally lies intermediate between slow- and fast-twitch limb skeletal muscles.
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U2 - 10.1152/jappl.1985.58.4.1085
DO - 10.1152/jappl.1985.58.4.1085
M3 - Article
C2 - 3988665
AN - SCOPUS:0021811837
SN - 8750-7587
VL - 58
SP - 1085
EP - 1091
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 4
ER -