Related Experiment Videos
Ca-activation and stretch-activation in insect flight muscle
Marco Linari1, Michael K Reedy, Mary C Reedy
1Laboratorio di Fisiologia, Dipartimento di Biologia Animale e Genetica, Università degli Studi di Firenze and Istituto Nazionale di Fisica della Materia, Firenze, Italy.
Biophysical Journal
|August 10, 2004
Summary
Insect flight muscles use calcium and stretch to activate force. Stretch activation complements calcium activation, allowing maximum force production through a shared cross-bridge mechanism.
Area of Science:
- Muscle physiology
- Insect biomechanics
- Skeletal muscle contraction
Background:
- Asynchronous insect flight muscle excels at oscillatory work but can also generate tetanic contractions.
- Understanding the interplay between calcium and mechanical stimuli is crucial for elucidating muscle function.
Purpose of the Study:
- To investigate the relationship between isometric force, calcium concentration, and stretch activation in insect flight muscle.
- To determine how stretch activation influences force production at different calcium levels.
Main Methods:
- Utilized skinned Lethocerus insect flight muscle fibers.
- Monitored sarcomere length using a striation follower.
- Measured isometric force (F(0)) at varying calcium concentrations ([Ca(2+)]) and the additional force (F(SA)) evoked by mechanical stretch.
Main Results:
- Isometric force increased with calcium, reaching maximum force (F(0,max)) between pCa 6.5 and pCa 8.
- Stretch activation (F(SA)) was dependent on baseline isometric force, requiring at least 0.05 F(0,max).
- F(SA) peaked when F(0) was ~0.2 F(0,max), and the sum of isometric and stretch-activated force remained constant (F(max)).
Conclusions:
- Calcium and stretch activation are complementary, activating a common cross-bridge mechanism.
- Stretch may relieve tropomyosin steric hindrance on actin, enabling maximal force at lower calcium levels.