Effect of actin microfilament on potassium current in guinea pig gastric myocytes

Whole-cell recordings of calcium and potassium currents in acutely isolated smooth muscle cells

AIM: To record calcium and potassium currents in acutely isolated smooth muscle cells of mesenteric arterial branches in rats.

METHODS: Smooth muscle cells were freshly isolated by collagenase digest and mechanical trituration with polished pipettes. Patch clamp technique in whole-cell mode was employed to record calcium and potassium currents.

RESULTS: The procedure dissociated smooth muscle cells without impairing the electrophysiological characteristics of the cells. The voltage-gated Ca²⁺ and potassium currents were successfully recorded using whole-cell patch clamp configuration.

CONCLUSION: The method dissociates smooth muscle cells from rat mesenteric arterial branches. Voltage-gated channel currents can be recorded in this preparation.

The association of caveolae, actin, and the dystrophin-glycoprotein complex: a role in smooth muscle phenotype and function?

Smooth muscle cells exhibit phenotypic and mechanical plasticity. During maturation, signalling pathways controlling actin dynamics modulate contractile apparatus-associated gene transcription and contractile apparatus remodelling resulting from length change. Differentiated myocytes accumulate abundant caveolae that evolve from the structural association of lipid rafts with caveolin-1, a protein with domains that confer unique functional properties. Caveolae and caveolin-1 modulate and participate in receptor-mediated signalling, and thus contribute to functional diversity of phenotypically similar myocytes. In mature smooth muscle, caveolae are partitioned into discrete linear domains aligned with structural proteins that tether actin to the extracellular matrix. Caveolin-1 binds with beta-dystroglycan, a subunit of the dystrophin glycoprotein complex (DGC), and with filamin, an actin binding protein that organizes cortical actin, to which integrins and focal adhesion complexes are anchored. The DGC is linked to the actin cytoskeleton by a dystrophin subunit and is a receptor for extracellular laminin. Thus, caveolae and caveolin-associated signalling proteins and receptors are linked via structural proteins to a dynamic filamentous actin network. Despite development of transgenic models to investigate caveolins and membrane-associated actin-linking proteins in skeletal and cardiac muscle function, only superficial understanding of this association in smooth muscle phenotype and function has emerged.