Water Loss during Contracture of Muscle

The relationship of contracture and exudation of water in frozenthawed frog muscle was studied. With maximum shortening, there was a water loss of 35 per cent of the weight of muscle. By restricting the contraction, it was demonstrated that the amount of water loss was proportional to the degree of shortening, there being no significant loss with isometric contraction. Muscle already shortened by tetanic stimulation also exuded water on subsequent freezing and thawing. The force of contraction could be reduced by depleting the muscle of calcium and it was shown that the amount of water exuded was also proportional to the tensile ability of the muscle. In a smooth muscle (anterior byssus retractor of Mytilus) which did not contract vigorously only a little water exuded. Contracture produced by caffeine was similarly associated with a loss of water. Microscopic studies revealed a disruption of the sarcomeres of the frozen-thawed muscle which contracted; glycerol-extracted and calciumdepleted muscles, which did not contract on freeze-thawing, did not show such disruption. Freezing and thawing of actomyosin caused a reversible syneresis of the protein. It is concluded that the exudation of the water is not merely due to the freezing and thawing but is also dependent on the contractile events. I N T R O D U C T I O N I t is well known tha t syneresis of actomyosin occurs when it is "superprecipit a t ed" with A T P (1). Likewise, water is lost dur ing contract ion of both freshly homogenized (2) and glycerol-extracted muscle fibers (3). In the l ight of these par t icular findings and on other general grounds, Szent-Gy6rgyi suggests tha t water is an integral par t of the contracti le system (4). Nevertheless, no fur ther direct evidence relat ing to this idea has been forthcoming. I t is well, however, to recall and reconsider the early observations repor ted by H e r m a n n on frozen-thawed muscle (5). In this prepara t ion eontrac ture follows on the thawing and is associated with exudat ion of water. Wh e t h e r this exudat ion is only a result of disruption of tissue barriers due to freezing and thawing, or whether it m a y have some relationship to the contracti le events, forms the subject of s tudy in the present investigation.