抄録
1. It is observed that the isometric contraction of the glycerol-treated fiber in a bath containing ATP and Mg++ is reversed to a considerable extent by mere washing, while the fiber contracted under isotonic conditions remains shortened upon washing.
2. A previous report (4) has stated that the fiber relaxed in a bath of EDTA, ATP and Mg++ can be made to contract upon addition of Cd++ or Zn++, but that the fiber relaxes again spontaneously when the concentration of Cd++ or Zn++ added exceeds that of the EDTA present. In contrast with these observations under isometric conditions, the second relaxation by Cd++ or Zn++ is not observed.
3. The pyrophosphate relaxation of the fiber under isometric conditions requires a concentration of pyrophosphate much lower and proceeds faster than that under isotonic conditions.
4. The cysteine-lengthening of the fiber under isotonic conditions can be stopped by addition of Cd++ or Zn++. The fiber thus ceased its lengthening retains the full recontractility.
5. A discussion is made on a temporary suggestion of the cross-linkage formation in the fiber under isotonic conditions.
