In vivo effects of snake venoms on passive and facilitated glucose transport across blood-ocular and blood-CSF barriers of the rat.
The transport of (3H)-3-0-methyl-D-glucose (mD-glu) and (14C)-L-glucose (L-glu) across blood-ocular and blood-CNS barriers was studied in rats with previously introduced (i.v.) lethal doses of lyophilized venom from one of three venomous snakes; mojave rattlesnake, Crotalus scutulatus; cottonmouth mocassin, Agkistrodon piscivorus; yellow cobra, Naja nivea. Transport rate constants calculated for mD-glu are taken as an indication of carrier-mediated transport, whereas L-glu constants are considered a measure of passive barrier permeability. C. scutulatus venom increased L-glu transport (+121%) across the blood-vitreous barrier. A passive increase in blood-vitreous permeability was also observed with mD-glu. This venom also increased passive L-glu entry rate into CSF (+160%). A. piscivorus venom also increased passive L-glucose entry into vitreous. However, whereas rattlesnake venom had little effect on blood-aqueous transport, cottonmouth venom may have also decreased carrier transport across this barrier. In addition, mD-glu transport from blood into CSF is decreased, suggesting a loss of carrier function across this barrier. N. nivea venom decreased the transport of both L-glu and mD-glu across the blood-aqueous, blood-vitreous and blood-CSF barriers, suggesting a possible decrease in cerebral blood flow as causative. There is also a possible increase in passive transport across the vitreous barriers, which may be in part countered by the decreased blood flow. Transport from aqueous into lens and cornea remained unchanged by the three venoms tested. It is suggested that components of rattlesnake and cottonmouth venoms alter transport barrier properties, with the blood-vitreous barrier being most susceptible to damage, whereas cobra venom likely decreases the supply of blood-borne substances to brain and ocular fluids and tissues by decreasing cerebral blood supply.
D019325:3-O-Methylglucose; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism*; D001812:Blood-Brain Barrier / Q000187:drug effects*; D003315:Cornea / Q000378:metabolism; D005123:Eye / Q000378:metabolism*; D005947:Glucose / Q000134:cerebrospinal fluid*; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism; D008757:Methylglucosides / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012910:Snake Venoms / Q000494:pharmacology*
D001786:Blood Glucose; D008757:Methylglucosides; D012910:Snake Venoms; D019325:3-O-Methylglucose; D005947:Glucose