CILIARY BEATING OF SCHISTOSOMA MIRACIDIUM-POSSIBLE INVOLVEMENT OF CYCLIC NCLEOTIDE AND ION CHANNEL

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The studies on regulation of ciliary motility in Paramecium encouraged us to investigate the control mechanisms of ciliary beat of schistosome miracidia. The present study aimed at investigating the possible involvement of cAMP,cGMP,protein kinase A and ion channels in signal transduction mechanisms of ciliary beat of schistosome miracidia.Schistosome miracidia swim in water by means of numerous cilia which cover the body surface. The miracidia stop swimming in 1% NaCL solution. Addition of membrane permeable cAMP or cGMP causes about 40% of miracidia to swim under high osmotic pressure, the swimming speed is about 1/6 of that of miracidia swimming in water though. Addition of forskolin, an activator of adenyl cyclase and guanyl cyclase, and IBMX,an inhibitor or phosphodiesterase also caused miracidial forward swimming. The effect of these reagents was dose dependent.Cholera toxin increases adenyl cyclase activity of metazoan via tis effect on G-protein. However, cholera toxin did not have any effect on ciliary beat of miracidia. Inhibitor of protein kinase A,H88 and H89, inhibited miracidial swimming in water. K^+channel blocker, quinine and alpha dendrotixin, caused swimming of miracidia in water. Inhibitory effect of H88, H89, quinine and alpha dendrotoxin was dose dependent. Na^+channel blocker and Ca^<++>channel blocker did not have any effect on swimming of miracidia.These results suggest that cyclic nucleotide, protein kinase A and K^+channel regulate ciliary beat of schistosome miracidia.