Steroid toxins

Two recent publications provide new and provocative input to this dialogue. One of these involved a series of appearances of a reddish substance on the East Coast called Chinese Love Stone, Black Stone, Rock Hard or Stud 100, being sold as aphrodisiacs. They were to be moistened and rubbed on the genitals, but as might be expected, quite a few were eaten and eventually smoked. They contained steroidal toxins, and were possibly related to some frog origins, but they were claimed to be bufotenine and indeed contained bufotenine in addition to several cardiotoxins as well as 5-MeO-DMT. 

The toxin acts on nerves to block transmissions to the muscle by increasing the permeability of membranes to sodium ions. It is specifically antagonized by tetro-dotoxin (Fig. 30-16). Batrachotoxin alkaloids are present also in certain birds.3303 Some echinoderms make powerful steroid toxins such as holothuiin A (Fig. 22-12), a surface active agent that causes irreversible destruction of the excitability of neuromuscular tissues. The common toad produces in its skin steroid toxins such as bufotoxin (Fig. 22-12), which are sufficiently powerful to teach a dog to leave toads alone. 

Figure 23.19 This Giant Marine toad uses a steroid toxin caiied bufotoxin as a defense mechanism. The toxin is fatai to some animais, inciuding dogs and cats. 

Several arthropods are rich sources of steroidal defensive compounds. These progestagens are particularly common in water beetles of the subfamilies Colymbetinae and Dytisci-nae. Beetles of these families accumulate steroidal toxins as... 

Other compounds present in the toxic secretion of peacock sole are glycosides of steroid toxins called pavoninins (10-259 to 10-262). The skin secretion of a related fish species known as finless sole (P. marmoratus) are structurally related lipophilic toxins called mosesins (10-259,10-260 and 10-262). 

Treatment — Because patients generally are exposed to small amounts of S. enterotoxin B toxin as a result of eating contaminated food (e.g., ham, salads with mayonnaise, and unrefrigerated cream dishes), they often have some protective antibodies. However, if the antibodies are overwhelmed by a terrorist-induced dosage, treatment with steroids should mollify patients symptoms. Further treatment would be supportive care, especially compensating for oxygen and fluid losses. While no vaccines are available, experimental vaccines in development have shown promise.3... 

Although most insects are flexible about their steroid sources, senita flies definitely are not They lack a set of enzymes indispensable for utilizing most steroids, cholesterol included. The enzymes they do have can handle only a few rare natural steroids, and only with these unusual compounds as starting points can they produce their own essential steroids. The single Sonoran source of these rare steroids seems to be senita cactus, and thus senita flies must incorporate the cactus into their diets or perish. As the only Sonoran fruit flies resistant to senita toxins, senita flies experience no competition from their relatives for the one plant that keeps them alive. 

Gaffield, W. and Keeler, R.F. (1996). Steroidal alkaloid teratogens molecular probes for investigation of craniofacial malformations, J. Toxicol. Toxin Rev., 15, 303-326. 

In addition to the receptors mentioned in A, the family of steroid receptors also includes the product of the oncogene erb-A (see p. 398), the receptor for the environmental toxin dioxin, and other proteins for which a distinct hormone ligand has not been identified (known as orphan receptors ). Several steroid receptors—e. g., the retinoic acid receptor-form functional heterodimers with orphan receptors. 

The purpose of the venom is offensive while that of a poison is defensive, which in turn influences the characteristics of the toxin. Venoms, either large or small molecules, are usually variants of essential biological molecules such as lipids, steroids, histamines or other proteins. They are often mixtures with a specific mechanism of action such as paralyzing the nervous system. Poisons are designed to teach a predator that this is not a good meal. They usually cause more localized pain to discourage a predator, but depending on the dose and sensitivity of the individual, the poison can be deadly. 

Bufogenins or Bufagins These are nitrogen-free steroidal lactones that are heart toxins found in toad venom. They have no chemical resemblance to bufotenine whatsoever. 

The steroid derivative ouabain (pronounced wah -bane from waa bayyo, Somali for arrow poison ) is a potent and specific inhibitor of the Na+K+ ATPase. Oubain binds preferentially to the form of the enzyme that is open to the extracellular side, locking in two Na+ ions and preventing the changes of conformation necessary to ion transport. Another very potent toxin, palytoxin (produced by a coral on the Hawaiian shoreline), also targets the Na+K+ ATPase, but it binds... 

---