The contractile vacuole and its membrane dynamics.

The contractile vacuole (CV) is an osmoregulatory organelle whose mechanisms of function are poorly understood. Immunological studies in the last decade have demonstrated abundant proton-translocating V-type ATPases (V-ATPases) in its membrane that could provide the energy, from proton electrochemical gradients, for moving ions into the CV to be followed by water. This review emphasizes recent work on the contractile vacuole complex (CVC) of Paramecium including (1) CV expulsion, (2) a role for V-ATPases in sequestering fluid, (3) identifying ions in the cytosol and in the CV, (4) in situ electrophysiological parameters of the CVC membrane, and (5) a better understanding of the membrane dynamics of this organelle.