Oxytocin-mediated recruitment of slowly cycling cross bridges and isometric force in rat myometrium

Andre L. Ruzycky, Bill T. Ameredes

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The relationship between cross-bridge cycling rate and isometric stress was investigated in rat myometrium. Stress production by myometrial strips was measured under resting. K+ depolarization, and oxytocin-stimulated conditions. Cross-bridge cycling rates were determined from measurements of maximal unloaded shortening velocity, using the quick-release method. Force redevelopment after the quick release was used as an index of cross-bridge attachment. With maximal K+ stimulation, stress increased with increased cross-bridge cycling (+76%; P < 0.05) and attached cross bridges (+112%; P < 0.05). Addition of oxytocin during K+ stimulation further increased stress (+30%; P < 0.05). With this force component, the cross-bridge cycling rate decreased (-60%; P < 0.05) similar to that under resting conditions. Attached cross-bridges did not increase with this additional stress. The results suggest two distinct mechanisms mediating myometrial contractions. One requires elevated intracellular calcium and rapidly cycling cross bridges. The other mechanism may be independent of calcium and appears to be mediated by slowly cycling cross bridges, supporting greater unit stress.

Original languageEnglish (US)
Pages (from-to)E203-E208
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number2 33-2
StatePublished - 1996
Externally publishedYes


  • myometrial contractility
  • potassium
  • protein kinase C
  • shortening velocity
  • slack test

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)


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