Receptor-mediated toxicity of pahutoxin, a marine trunkfish surfactant.
Pahutoxin (PHN, choline chloride ester of 3-acetoxypalmitic acid) is a natural fish-killing (ichthyotoxic) agent derived from the defensive secretions of trunkfish. In spite of its obvious structural resemblance to synthetic cationic long-chain quaternary ammonium detergents, we show that PHN's action does not rely on its surfactant properties and is in fact, receptor-mediated. The above conclusion is supported by the following data: 1. Ichthyotoxicity is not related to its detergency or surfactivity, as indicated by the fact that the lethal concentration is about 1.5 orders of magnitude below its critical micelle concentration value (69 microM) and its liposomal/seawater partition coefficient is low (62-85); 2. The trunkfish is tolerant to its own pahutoxin; 3. Ichthyotoxicity occurs only upon application to the surrounding water, suggesting the existence of externally located receptors; 4. The receptor hypothesis was supported by the aid of equilibrium saturation binding assays revealing the presence of specific binding sites to PHN on the fish gill membranes; 5. The PHN tolerant trunkfish was shown to be devoid of PHN-binding sites. Some chemo-ecological, and environmental implications are discussed.
Kalmanzon
Eliahu
E
Department of Animal and Cell Biology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Rahamim
Yocheved
Y
Barenholz
Yechezkel
Y
Carmeli
Shmuel
S
Zlotkin
Eliahu
E
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002794:Choline / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000633:toxicity*; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D007928:Lethal Dose 50; D008081:Liposomes / Q000378:metabolism; D008387:Marine Toxins / Q000302:isolation & purification / Q000633:toxicity*; D008823:Micelles; D021541:Sea Bream / Q000502:physiology; D012995:Solubility; D013501:Surface-Active Agents / Q000633:toxicity*; D023721:Tetraodontiformes / Q000378:metabolism*
D008081:Liposomes; D008387:Marine Toxins; D008823:Micelles; D013501:Surface-Active Agents; C052962:pahutoxin; D002794:Choline