>>PHOSPHOLIPASE A - Promotes histamine production in tissue. Also probably largely responsible for the "shock factor" encountered in snakebite. (S/E: Black Mamba, Taipan, cottonmouth)



Hi Wolfgang,



I believe the thinking behind that quote dates to the 1940’s when histamine was felt to be the major mediator of shock. It was during this period that researchers were using snake venoms to study inflammatory mechanisms and their roles in producing shock. Recall that the term “shock”, in a clinical context, describes a state in which there is inadequate supply of blood / oxygen to vital organs due to a severe disturbance in blood volume, blood location, or blood pumping (or a combination of these). Blood pressure is the most easily measurable marker to determine presence or absence of shock. Anyhow, in these early investigations into inflammation / shock, certain snake venoms were shown to cause hypotension / shock in animals, and analysis of venous blood from “venom-shocked” animals consistently showed elevated histamine levels, suggesting histamine might play a role in shock, and that venoms contained histamine releasing activity. Later experiments showed certain PLA2s in certain venoms produce mast cell degranulation in a nonspecific fashion. I suspect this is why phospholipase (or perhaps even histamine) is referred to as “shock factor” in the old excerpt provided by Bud.



Budman, from where did you get that excerpt, if you don’t mind me asking?



Cheers,

WK

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