9505567 Goldstein Body cells must maintain their volume constant in order to function properly. Both humans and animal cells face constant threats to their volumes under both physiological and pathological conditions. In this proposal, Dr. Goldstein will be examining the cellular and molecular mechanisms that permit cells to maintain constant volume in the face of osmotic disturbances in the environment surrounding cells. The experimental model will be the red blood cell of the skate. He has used this model successfully in the past to begin elucidating the physiological processes in the cell membrane that are involved in adjusting cell volume back to normal after extracellular disturbances. He will continue with these studies as well as others that deal with the ways in which cell volume changes are signaled to volume-adjustilg mechanisms operating in the cell membrane. The studies will lead to a better understanding of the physiological basis of the fundamethal phenomemon of cell volume regulation. ***