title: Action on ileal smooth muscle of synthetic detergents and pardaxin.
abstract: Pardaxin (PX), a toxic and repellent substance isolated from the Red Sea flatfish, causes a sharp ball-like profile of drop of saline placed on a hydrophobic film to turn into a flattened one. This effect results with a decrease of the contact angle (theta) from 96 degrees to a maximum of 42 degrees at 10(-4) M of PX. The action of sodium dodecyl sulphate (SDS), a synthetic anionic detergent, benzalkonium chloride (BAC) cationic detergent and pardaxin (PX) a toxic protein with detergent properties, were studied in the ileal guinea-pig longitudinal smooth muscle preparation. SDS (4 X 10(-4) M) and PX (5 X 10(-6) M) diminished the muscle contractile response to field stimulation (0.1 Hz, 1 msec) and to acetylcholine (Ach) and to histamine and elicited a prolonged (4-6 min) TTX-insensitive muscle contraction. The dose dependence of muscle contraction to SDS and PX was found to be sigmoidal and occurred over a narrow range of concentrations. The SDS- but not PX-induced muscle contraction could be reduced by diphenhydramine (H1 antihistamine). BAC (10(-5)-10(-4) M) suppressed the muscle's contractile response to electrical stimulation (0.1 Hz, 1 msec), to Ach, histamine and 5-hydroxytryptamine but did not produce muscle contraction. PX at concentrations higher than 5 X 10(-6) M is a potent detergent and at this concentration shares several pharmacological similarities with SDS.
mesh_terms: D000818:Animals; D001548:Benzalkonium Compounds / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology*; D004155:Diphenhydramine / Q000494:pharmacology; D005397:Fish Venoms / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D001548:Benzalkonium Compounds; D003902:Detergents; D005397:Fish Venoms; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; C017603:pardaxin; D004155:Diphenhydramine