Tc 99m - SCORPION VENOM: LABELLING, BIODISTRIBUTION AND SCINTIIMAGING

Abstract

Labelling of scorpion (Mesobuthus tamulus concanesis Pocock) venom was successfully achieved with Tc 99m using direct tin reduction procedure. Biodistribution studies were carried out in Wistar rats at different time intervals after i.v. administration of the labelled venom. Scintiimages were obtained after scorpion envenoming using a large field of view gamma camera to ascertain the pharmacological action of venom in the body. Within 5 min of administration, labelled venom was found in the blood (27.7%), muscle (30.11%), bone (13.3%), kidneys (11.5%), liver (10.4%), and other organs. The level of venom in the kidneys was higher than in the liver. The labelled venom was excreted through renal and hepatobiliary pathways. An immunoreactivity study was carried out in rabbits after i.v. injection of labelled scorpion venom followed by the injection of the species specific antivenom. A threefold increase in uptake by the kidneys was observed compared with that seen with scorpion venom alone. The neutralisation of the venom in the kidneys was higher than in the liver

Comparison of two purified toxic fractions from Mesobuthus eupeus scorpion venom

“…The mixtures were incubated for 20 minutes at room temperature under vacuum conditions. After this period, 1 mL of saline solution was added to reaction vials (0.5 mL in each vial) in order to interrupt the labeling reaction (16,17). The scheme of direct labeling with 99m Tc is displayed in Figure1.…”

Cardiorespiratory evaluation of juvenile rats experimentally envenomed with Tityus serrulatus venom

“…Venom levels were maximal at 30 minutes after administration; after two hours of experiment these concentrations plummeted, and no venom could be detected in any tissue at eight hours after envenomation. Radioactivity tracer experiments using technetium-99 showed that Mesobuthus tamulus venom could be detected in the lungs of rats at five minutes after envenomation (35). Such a rapid distribution of the venom in the lungs, together with intense pulmonary hemorrhage, support the hypothesis that the venom has a direct action on organs and ultimately leads to development of pulmonary edema and impairment of the cardiac function, as observed in classical scorpion envenomation syndrome.…”

In vitro studies with renal proximal tubule cells show direct cytotoxicity of Androctonus australis hector scorpion venom triggered by oxidative stress, caspase activation and apoptosis

“…In fact, in experimental animals the level of venom in blood declines as much as 6 fold within 1 hour after administrating venom [26]. During this time, the venom is redistributed to other tissues [26].…”

“…During this time, the venom is redistributed to other tissues [26]. Kidney tissue accumulates the largest concentration of venom after this redistribution, and because this is coupled with a slow removal rate of venom, the exposure of renal tissue to venom may be of a duration as prolonged as in the experiments described in this report [26–28].…”

“…During this time, the venom is redistributed to other tissues [26]. Kidney tissue accumulates the largest concentration of venom after this redistribution, and because this is coupled with a slow removal rate of venom, the exposure of renal tissue to venom may be of a duration as prolonged as in the experiments described in this report [26–28]. Moreover, venom toxins can achieve very high tissue concentrations after their redistribution from the blood to other tissues, particularly the kidney, and thus have the potential to cause direct toxicity [19].…”