title: Factors in snake venoms that increase capillary permeability.
abstract: Capillary permeability increasing (CPI) activity is a phenomenon of the microvasculature caused by many agents such as snake venoms, histamine, 5-hydroxytryptamine (5-HT), prostaglandins and leukotrienes. Since no systematic study has been done to determine what components of snake venom cause CPI activity, a CPI factor from Naja naja atra (Taiwan cobra) venom was isolated using intravenous injections of Evan's blue dye as the indicator of increased permeability and the factor's properties were extensively studied. Cardiotoxin from Naja naja kaouthia (Thailand cobra) and Mojave toxin from Crotalus scutulatus scutulatus (Mojave rattlesnake) venoms demonstrated CPI activity. Postsynaptic neurotoxins from an elapid and a hydrophid and myotoxin a from Crotalus viridis viridis (prairie rattlesnake) showed no CPI activity at the dose studied. The purified CPI active component from Naja naja atra venom was found to have cardiotoxic activity. Therefore, Elapidae cardiotoxins are CPI active factors. However, CPI activity is not due to cardiotoxins alone as the presynaptic neurotoxin, Mojave toxin, also showed CPI activity. Selective inhibitors were used to indicate possible mechanisms of action on the capillaries by Naja naja atra venom and Crotalus scutulatus scutulatus venom. The histamine H1-receptor blockers diphenhydramine, promethazine, and cyproheptadine were effective against both venoms in preventing increased capillary permeability. These results suggested that histamine release activity is the most likely mechanism resulting in CPI activity from these venoms.
authors.affiliation: Department of Biochemistry, Colorado State University, Fort Collins 80523.
authors.forename: R A
authors.initials: RA
authors.lastname: Miller
authors.forename: A T
authors.initials: AT
authors.lastname: Tu
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects*; D003435:Crotalid Venoms / Q000494:pharmacology*; D004546:Elapid Venoms / Q000032:analysis / Q000494:pharmacology*; D007525:Isoelectric Focusing; D051379:Mice; D008970:Molecular Weight
chemical_list: D000596:Amino Acids; D003435:Crotalid Venoms; D004546:Elapid Venoms