Related Experiment Video
Updated: Oct 3, 2026

Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Published on: August 18, 2014
[New trends in studying the regulatory mechanism of smooth muscle contraction]
1Department of Pharmacology, Gunma University School of Medicine, Maebashi, Japan.
Abstract:
In this paper, we briefly review current topics about smooth muscle with regards to Ca2+ release, Ca2+ sensitization, and Ca2+ regulation of contraction. Inositol 1,4,5-trisphosphate releases Ca2+ from the sarcoplasmic reticulum, where Ca(2+)-dependent immediate feedback control may work. However, the involvement of this feedback control in the Ca(2+)-induced Ca2+ release mechanism remains to be elucidated. Either agonist or GTP gamma S is known to increase the Ca2+ sensitivity of myofilaments. The agonist-induced Ca2+ sensitization could be explained by the up-regulation due to myosin light chain kinase or by the down-regulation due to myosin light chain phosphatase. The GTP gamma S-induced Ca2+ sensitization seems to be mediated by rho A p21, a small G protein. Thus, myosin phosphorylation is not the obligatory way to regulate the actin-myosin interaction. We propose that cross-linking between actin and myosin may work as an alternative way to regulate the interaction from biochemical studies. The candidates for the cross-linkers are caldesmon, calponin and myosin light chain kinase. The inhibitory effect of Ca2+ on the interaction, which is observed under the specific conditions for measuring smooth muscle contraction, may hold the key to finding the physiological significance of the cross-linking activity.
More Related Videos
Related Concept Videos
Muscle Contraction
The Role of Actin and Myosin in Non-muscle Cells
Muscle Contraction
Nitric Oxide Signaling Pathway
Motor Unit Stimulation
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...

