Tentacle contraction in Heliophrya erhardi (Suctoria): the role of inositol phospholipid metabolites and cyclic nucleotides in stimulus-response coupling.
Extracellular stimulation of Heliophrya erhardi with 15 V, 100 ms induces tentacle contraction. The effects of a number of pharmacological agents on response latency (time from stimulus to start of contraction) and contraction time (time for tentacles to reach 20% of their original length) were recorded. Contraction was enhanced in the presence of phorbol ester TPA and R59022, both of which increase activation of diacylglycerol-dependent protein kinase C. Lithium ions, which are known to inhibit dephosphorylation of inositol 1-phosphate, also affected the response, causing a decrease in latency and increase in contraction time. These results strongly implicate products of inositol phospholipid metabolism in stimulus-contraction coupling. The latency of contraction was reduced in the presence of IBMX, a nonspecific inhibitor of cyclic nucleotide phosphodiesterases. Application of membrane-permeable cyclic nucleotide analogs led to an increase in latency and contraction time for cAMP analog, but a decrease in both parameters for cGMP. This suggests that the two cyclic nucleotides have opposing roles in modulating the response. The possible roles and interactions of membrane phospholipid metabolites and cyclic nucleotides in the control of tentacle contraction of H. erhardi are discussed.
Evans
R L
RL
Department of Cell and Structural Biology, University of Manchester, United Kingdom.
McCrohan
C R
CR
Butler
R D
RD
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000031:analogs & derivatives / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D016798:Ciliophora; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D003995:Dibutyryl Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D009119:Muscle Contraction; D011744:Pyrimidinones / Q000494:pharmacology; D013403:Sugar Phosphates / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
D002712:Chlorides; D007295:Inositol Phosphates; D011744:Pyrimidinones; D013403:Sugar Phosphates; D013844:Thiazoles; C002373:monobutyryl cyclic AMP; D003995:Dibutyryl Cyclic GMP; C040016:monobutyryl cyclic GMP; D003994:Bucladesine; C047505:R 59022; D008094:Lithium; D000242:Cyclic AMP; D018021:Lithium Chloride; D006152:Cyclic GMP; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine