Mechanotransduction in rat myometrium: coordination of contractions of electrically and chemically isolated tissues.

The generally accepted mechanism for global uterine coordination is propagation of electrical activity. Mechanotransduction mechanisms were briefly considered as a secondary mechanism 40 years ago, but scant data have appeared. Here, we provide evidence that tissue strips are capable of functionally interacting solely by mechanical mechanisms. We mechanically linked, in series, 2 rat myometrial strips of similar size. Strips were placed in separate baths to ensure they were electrically and chemically isolated. A force transducer was used to measure force production. We precisely determined when each tissue contracted by simultaneously measuring each strip's electrical activity using contact electrodes. We observed both in-phase and out-of-phase contraction patterns from the tissues. To determine whether modulation of the electrical properties of the tissue is involved in the mechanotransduction mechanism, we briefly stretched single tissue strips during alternate contractions. This technique provided a control contraction for each test contraction. The duration of the contraction that was stretched measured longer than the control in 33 of 35 pairs (P = .0001, Wilcoxon signed-rank test for paired data). Interestingly, briefly slackening the tissue also prolonged the force-producing phase of that contraction (39 of 42 pairs; P = .0006). Because our data show that mechanotransduction mechanisms coordinate tissue-level contractions, we speculate that mechanotransduction mechanisms may contribute to organ-level coordination of contractions.