Rhythmic contraction in the plasmodium of the myxomycete Physarum polycephalum in relation to the mitochondrial function.

Abstract

The plasmodium of the myxomycete Physarum polycephalum shows rhythmic contraction. The effect of mitochondrial inhibitors on this activity was examined. The separate inhibition of respiration or of H-F--ATPase activity or of ATP/ADP translocation failed to stop rhythmic contraction although the period of oscillation was affected. The concurrent inhibition of respiration and ATPase activity or the concurrent inhibition of respiration and ATP/ADP translocation, however, almost wholly suppressed contraction. Removal of respiratory inhibition in either case restored rhythmic contraction. The resumption of rhythmic activity occurred even though the ATP concentra-tion in the plasmodium remained at half the control level. Our results suggest that a particular mitochondrial state is indispensable for rhythmic contraction in Physarum polycephalum, and that this state influences rhythmic activities by means other than the control of the ATP level.