title: Modelling Tityus scorpion venom and antivenom pharmacokinetics. Evidence of active immunoglobulin G's F(ab')2 extrusion mechanism from blood to tissues.
abstract: Modelling Tityus scorpion venom and antivenom pharmacokinetics. Evidence of active immunoglobulin G's F(ab')(2) extrusion mechanism from blood to tissues. We measured pharmacokinetic parameters for T. discrepans venom in rams. Forty, 75 or 100 microg/kg venom were injected subcutaneously in the inner side of the thigh. Plasma venom content (venenemia) was determined by enzyme-linked immunosorbent assay (ELISA) from 0 to 300 min after injecting venom. Venenemia was fit to a three-compartment model (inoculation site, plasma and extra vascular extracellular space), it was assumed that the venom may also be irreversibly removed from plasma. Calculated time course of venom content shows that at any time no more that 30% of the venom is present in plasma. Venenemia peaks at 1h and decays afterwards. Fluorescently labelled antivenom [horse anti-TityusF(ab')(2) or fraction antigen binding, immuglobulin without Fc chain covalently bound to fluorescine or fluorescamine] pharmacokinetics was determined. Although F(ab')(2) molecular weight is >/=10 times bigger that toxin's, the rate of outflow of F(ab')(2) from blood to tissues was approximately 4 times faster than the venom's outflow. Venom content in the injection site decays exponentially for >6h, this prediction was confirmed immunohistochemically. Only approximately 5% of the venom is eliminated in 10h; approximately 80% of the venom is in the tissues after 2h and remains there for >10h.
authors.affiliation: Laboratory of Cellular Neuropharmacology, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 21827, Caracas 1020A, Venezuela.
authors.forename: C
authors.initials: C
authors.lastname: Sevcik
authors.forename: G
authors.initials: G
authors.lastname: D'Suze
authors.forename: P
authors.initials: P
authors.lastname: Díaz
authors.forename: V
authors.initials: V
authors.lastname: Salazar
authors.forename: C
authors.initials: C
authors.lastname: Hidalgo
authors.forename: H
authors.initials: H
authors.lastname: Azpúrua
authors.forename: N
authors.initials: N
authors.lastname: Bracho
mesh_terms: D000818:Animals; D000997:Antivenins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D005453:Fluorescence; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism*; D007074:Immunoglobulin G; D007150:Immunohistochemistry; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D012604:Scorpion Venoms / Q000097:blood / Q000493:pharmacokinetics*; D012605:Scorpions / Q000737:chemistry*; D012756:Sheep
chemical_list: D000997:Antivenins; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D012604:Scorpion Venoms