Control of intestinal motility by the Ca(v)1.2 L-type calcium channel in mice

Area of Science:

• Physiology
• Molecular Biology
• Gastroenterology

Background:

• The Ca(v)1.2 L-type Ca2+ channel is a key regulator of muscle contraction.
• Its role in intestinal smooth muscle, however, requires further elucidation.

Purpose of the Study:

• To investigate the functional significance of the Ca(v)1.2 gene in intestinal smooth muscle.
• To understand the Ca2+ sources for contraction in the absence of Ca(v)1.2 channels.

Main Methods:

• Generation and analysis of smooth muscle-specific conditional Ca(v)1.2 knockout mice (Ca(v)1.2SMACKO).
• Tamoxifen-induced gene inactivation.
• Confirmation of gene deletion via RT-PCR and Western blot.
• Functional assessment of intestinal muscle contractility.

Main Results:

• Ca(v)1.2SMACKO mice exhibited reduced feces excretion and signs of paralytic ileus.
• Absence of rhythmic contractions in small and large intestinal muscle.
• Ca(v)1.2 channels are the primary source of Ca2+ for electromechanical coupling in jejunum, with store-operated channels compensating partially for pharmaco-mechanical coupling.

Conclusions:

• The Ca(v)1.2 channel is essential for electromechanical and important for pharmaco-mechanical coupling in intestinal smooth muscle.
• Other Ca2+ entry pathways cannot fully substitute for Ca(v)1.2 channel function in maintaining intestinal motility.