Transformation of individual contractile responses during tetanus in rat fast and slow skeletal muscles
- Autores: Kubasov I.1, Arutyunyan R.1, Matrosova E.1
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Afiliações:
- Sechenov Institute of Evolutionary Physiology and Biochemistry
- Edição: Volume 52, Nº 1 (2016)
- Páginas: 46-55
- Seção: Comparative and Ontogenic Physiology
- URL: https://journals.rcsi.science/0022-0930/article/view/158984
- DOI: https://doi.org/10.1134/S0022093016010051
- ID: 158984
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Resumo
Using a computer graphics approach, the last contractile responses (LCRN, where N is a number of elementary contractile responses in tetanus) were separated from integral tetanic responses of rat fast muscles, m. Eхtensor digitorum longus (m. EDL), and slow muscles, m. Soleus, evoked by trains of 5, 10 and 50 stimuli. In m. Soleus, at a stimulation frequency of 20 Hz, the LCR5 average amplitude decreased to 64 ± 9% compared to the single contraction amplitude. As N increased, LCRN recovered and then rose to the values exceeding almost twofold initial elementary contractile responses (up to 211 ± 10% for LCR50). Simultaneously, against the background of rising elementary contractile responses, a significant shortening of their half-decay time (∼by 50%) and the formation of a stationary plateau within LCRN was observed. In m. EDL, at a stimulation frequency of 50 Hz, there was only a single-phase LCRN rise (up to 165 ± 18% for LCR50) without changes in half-decay time and plateau formation. In skeletal muscles of both types, the prolonged (up to 30 s) ‘hyper-relaxation effect’ was found to develop after the end of tetanic responses manifested as a reduction of muscle tension followed by its recovery to the initial level. Possible mechanisms of these events are discussed. It is hypothesized that transformation of elementary contractile responses in skeletal muscles can be fulfilled due to the existence of specialized microdomains in muscle fibers which regulate accumulation and extrusion of Ca2+ ions during tetanic activity. The possibility that the basic, depolarization-induced, Ca2+ release (DICR) is complemented by an additional, Ca2+-induced, Ca2+release (CIRC) is analyzed.
Sobre autores
I. Kubasov
Sechenov Institute of Evolutionary Physiology and Biochemistry
Autor responsável pela correspondência
Email: kubasov_igor@mail.ru
Rússia, St. Petersburg
R. Arutyunyan
Sechenov Institute of Evolutionary Physiology and Biochemistry
Email: kubasov_igor@mail.ru
Rússia, St. Petersburg
E. Matrosova
Sechenov Institute of Evolutionary Physiology and Biochemistry
Email: kubasov_igor@mail.ru
Rússia, St. Petersburg