THE CONTRACTILE VACUOLE FLUID DISCHARGE RATE IS DETERMINED BY THE VACUOLE SIZE IMMEDIATELY BEFORE THE START OF DISCHARGE IN PARAMECIUM-MULTIMICRONUCLEATUM
Y. Naitoh et al., THE CONTRACTILE VACUOLE FLUID DISCHARGE RATE IS DETERMINED BY THE VACUOLE SIZE IMMEDIATELY BEFORE THE START OF DISCHARGE IN PARAMECIUM-MULTIMICRONUCLEATUM, Journal of Experimental Biology, 200(12), 1997, pp. 1737-1744
The precise relationship between the rate of contractile vacuole fluid
discharge and the vacuole diameter at the start of systole was determ
ined in cells of Paramecium multimicronucleatum subjected to various e
xternal conditions. The rate of discharge was higher when the diameter
was larger. When the rate of discharge was plotted against the diamet
er, the points fell around a single parabolic line passing through the
origin and were independent of the external conditions employed. This
implies that the rate of discharge is proportional to the square of t
he vacuole diameter, We have previously proposed a hypothesis in which
membrane tension in the contractile vacuole is altered as its planar
membrane becomes tubular or as tubules become planar membrane (termed
the membrane area-proportional tension hypothesis), We propose here th
at it is this change in membrane tension which determines the vacuole
pore shape and sets the subsequent rate of fluid discharge.