Participation of native tropomyosin in the ATP-contraction of an intestinal glycerinated muscle bundle.

Observations were made on the Ca-sensitivity of glycerinated muscle bundles from dog intestine. The results obtained were as follows 1) The Ca-sensitivity of glycerinated muscle bundles depends on theduration of glycerol extraction. With long-term extraction, the muscle bundles lost a large part of the Ca-sensitivity of the ATP contractility. 2) When the bundles that had a typical Ca-sensitivity were treated with a low concentration of trypsin, their ATP-contractility became insensitive to varying concentrations of Ca ions. 3) On treatment with intestinal native tropomyosin, the Ca-sensitivity of the ATP-contractility of 2-year-glycerinated muscle bundles was restored, to a certain extent. With the same treatment, the Ca-sensitivity of trypsin-treated 2-year-glycerinated muscle bundle was restored to the same level as that of 2-year-glycerinated bundles. From these results, it is concluded that the Ca-sensitivity of the ATP-contractility of intestinal glycerinated muscle is due to the native tropomyosin it contains.