It is well known that the overlap between the thick and thin filaments in striated muscle is responsible for the single active length-tension (L-T) curve. With the lack of visible striations, a sarcomeric unit has not been identified in smooth muscle. Though once thought to function like striated muscle via a sliding filament mechanism of contraction, recent studies on length-adaptation (L-adaptation) in airway smooth muscle (ASM), in which increased tension is generated with repeated contraction, have led to the hypothesis of a dynamic L-T curve in smooth muscle. Although more established in ASM, two studies have shown L-adaptation in vascular smooth muscle (VSM). In this project, the L-T curve over a 3-fold length range in rabbit femoral artery was investigated and the presence of more than one active and passive L-T curve was identified. The third of three repeated KCL-induced contractions at a single, shortened length resulted in L-adaptation in which the phasic and tonic phases of contraction demonstrated a 10-15% increase in active tension (Ta) relative to the first contraction. Experiments investigating possible mechanism(s) responsible for this phenomenon demonstrated that neither an increase in [Ca2+]i nor an increase in MLC20 phosphorylation was responsible for the increased tension. However, actin polymerization did appear to play a role in the L-adaptation of both phases of contraction. Thus directions for future research could include further study of actin polymerization in VSM that contributes to L-adaptation and may ultimately result in artery remodeling.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-2884 |
| Date | 22 July 2009 |
| Creators | Bednarek, Melissa |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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