MECHANICAL DETERMINANTS OF ISOTONIC RELAXATION IN ISOLATED DIAPHRAGM MUSCLE

被引:19
作者
COIRAULT, C
CHEMLA, D
PERY, N
SUARD, I
LECARPENTIER, Y
机构
[1] HOP BICETRE,UER PARIS 11,SERV PHYSIOL,78 RUE GEN LECLERC,F-94275 LE KREMLIN BICETR,FRANCE
[2] ECOLE POLYTECH,ENSTA,LOA,INSERM,U275,F-91128 PALAISEAU,FRANCE
关键词
MECHANICS OF SKELETAL MUSCLE; RESPIRATORY MUSCLE;
D O I
10.1152/jappl.1993.75.5.2265
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Determinants of lengthening velocity have not been investigated in the diaphragm muscle. This study was undertaken to define the mechanical determinants of isotonic relaxation rate over the entire load continuum in isolated rat diaphragm (n = 30). We tested the hypothesis that the determinants of lengthening could include loading conditions, namely, preload and after-load; abrupt changes of load during the contraction phase; end-shortening muscle length (ESL); extent of shortening (DELTAL); time; stimulation mode; and stimulation frequency. In after-loaded contractions preloaded at optimal initial length and stimulated in tetanus at 30 Hz, peak lengthening velocity (+dL/dt(max)) was linearly related to DELTAL, ESL, and/or total load. Varying initial muscle length, ESL, afterload, or the load imposed on the muscle during the isotonic lengthening process did not modify +dL/dt(max) vs. DELTAL relationship, whereas +dL/dt(max) vs. load and +dL/dt(max) vs. ESL relationships were modified by these procedures. For a given DELTAL, +dL/dt(max) could be modified when lengthening was delayed by reversing the relaxation sequence and when twitch and tetanus modes were compared. In conclusion, our results demonstrate that in isolated diaphragm muscle, DELTAL is the main determinant of +dL/dt(max) over a wide range of loads and under various experimental conditions, independent of ESL and initial muscle length and independent of the load imposed on the muscle during the lengthening process. Time and stimulation mode were also shown to modulate the lengthening rate in diaphragm muscle.
引用
收藏
页码:2265 / 2272
页数:8
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