Inhibition of force and shortening in smooth muscle by vanadate
Pflugers Archiv European Journal of Physiology, cilt.438, sa.2, ss.224-231, 1999 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 438 Sayı: 2
- Basım Tarihi: 1999
- Doi Numarası: 10.1007/s004240050902
- Dergi Adı: Pflugers Archiv European Journal of Physiology
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Sayfa Sayıları: ss.224-231
- Anahtar Kelimeler: Actin-myosin interaction, Internal load, Myosin light chain phosphorylation, Smooth muscle contraction, Vanadate
- Maltepe Üniversitesi Adresli: Hayır
Özet
We have investigated the effects of vanadate (V(i)) on force generation by, and shortening of, chemically skinned smooth muscle preparations from guinea-pig taenia coli at 22°C. A method, using phosphatase inhibitors, was introduced to obtain stable, long-lasting contractions in thiophosphorylated preparations. V(i) (10-1000 μM) dose-dependently inhibited active force, to about 20% of its maximum level. At a higher temperature (30°C), the rate of inhibition was faster but the extent of inhibition was less. The rate of contraction following photolytic release of ATP to fibres in rigor was not affected by V(i) (30 μM). The maximal shortening velocity (V(max)) was inhibited in a similar manner as active force by V(i) (30 μM). In conclusion, the results suggest that V(i) interacts with a force-generating actomyosin-ADP (AMADP) state reached after phosphate release. The rate of inhibition of smooth muscle contraction was markedly lower than in skeletal muscle, suggesting differences either in properties of the V(i)-bound states or, more likely, in the concentration of AMADP states capable of binding V(i). This suggests that the long duty cycle in smooth muscle is not associated with a higher relative population of AMADP states reached immediately after P(i) release, but rather by an increase in the population of subsequent force-generating cross-bridge states. The V(i)-bound cross- bridges introduce an internal load to shortening, possibly acting in a similar manner as cross-bridge states introduced at low levels of activation.