ISOSMOTIC INTRACELLULAR REGULATION AS A MECHANISM OF VOLUME CONTROL IN CRAB MUSCLE FIBERS

1. 1. Muscle fibers swollen in hypotonic sodium salines undergo spontaneous decreases in volumes (volume-readjustment) towards he initial volumes of the cells found in isotonic salines. 2. 2. This volume-readjustment is due to the elimination of osmotically active particles from the intracellular space of the muscle fibre. 3. 3. The only major intracellular solutes which were significantly lost from blue crab muscles as a result of volume-readjustment were the non-protein ninhydrin-positive substances. 4. 4. It is proposed that this component represents a fraction of the large intracellular pool of free amino acids found in crab muscle, and that free amino acids are being actively transported out of the muscles during volume-readjustment. 5. 5. Results of preliminary studies on the efflux of 2-aminoisobutyric acid-1-14C from crab muscles are consistent with the view that amino acids are being actively transported out of the muscle cells during volume readjustment. © 1969.