The Journal of Cell Biology, Vol 100, 1447-1454, Copyright © 1985 by The Rockefeller University Press
Calcium control of ciliary reversal in ionophore-treated and ATP- reactivated comb plates of ctenophores
S Nakamura and SL Tamm
Previous work showed that ctenophore larvae swim backwards in high-KCl
seawater, due to a 180 degrees reversal in the direction of effective
stroke of their ciliary comb plates (Tamm, S. L., and S. Tamm, 1981, J.
Cell Biol., 89: 495-509). Ion substitution and blocking experiments
indicated that this response is Ca2+ dependent, but comb plate cells are
innervated and presumably under nervous control. To determine whether Ca2+
is directly involved in activating the ciliary reversal mechanism and/or is
required for synaptic triggering of the response, we (a) determined the
effects of ionophore A23187 and Ca2+ on the beat direction of isolated
nerve-free comb plates dissociated from larvae by hypotonic, divalent
cation-free medium, and (b) used permeabilized ATP- reactivated models of
comb plates to test motile responses to known concentrations of free Ca2+.
We found that 5 microM A23187 and 10 mM Ca2+ induced dissociated comb plate
cells to beat in the reverse direction and to swim counterclockwise in
circular paths instead of in the normal clockwise direction.
Detergent/glycerol-extracted comb plates beat actively in the presence of
ATP, and reactivation was reversibly inhibited by micromolar concentrations
of vanadate. Free Ca2+ concentrations greater than 10(-6)M caused reversal
in direction of the effective stroke but no significant increase in beat
frequency. These results show that ciliary reversal in ctenophores, like
that in protozoa, is activated by an increase in intracellular free Ca2+
ions. This allows the unique experimental advantages of ctenophore comb
plate cilia to be used for future studies on the site and mechanism of
action of Ca2+ in the regulation of ciliary motion.
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