Cyclodiene Insecticide Michelle Nakamura Biol 468

 Aldrin (C 12 H 8 Cl 6 )  MW:  Appearance:  Pure – white powder  Commercial grade – tan powder  Low water solubility (< 27 ng/L)  No reaction with water  Hydrophobic! (log K ow = 7.4)  Highly soluble in fats, waxes, oils, and other organic solvents

 Uses and Applications  Pesticide for soil and crops -mostly corn, some cotton  Termite control  Does not occur naturally in the environment  1950s s: widely used as an insecticide  1987: EPA banned all uses of aldrin

 Atmospheric deposition  Does not leach into the groundwater, but will volatilize off the fields  High wind dispersal  Some river runoff

 Photo-oxidation  Sunlight degrades aldrin to dieldrin  Physical half-life: years

 Mode of entry into organism  Direct contact (gills, epidermis)  Ingestion  96h LC 50 (for fish): 2-53 µg/L  Toxic effects noted:  Damage to the central nervous system ▪Convulsions  Liver cancer

 Aldrin competes with GABA molecules for the binding site on the GABA receptor  When GABA binds, Cl- channels open, inhibits firing of new action potentials  When aldrin binds, Cl- channels stay closed, action potentials keep firing * INCREASES pre-synaptic neurotransmitter release!

 Aldrin is rapidly converted to dieldrin by CYP450 found on the endoplasmic reticulum of liver cells  Biotransformation takes only hrs  Result: very little aldrin found in the blood or tissues  Mediated by the mixed-function mono-oxygenase (MFO) system

 Biotransform aldrin  dieldrin  Dieldrin is slightly more polar than aldrin, but is still hydrophobic  Bioaccumulates in fatty tissues

 Soil pesticide for crops  No longer produced  Hydrophobic  Can be absorbed by direct contact or ingestion  Causes convulsions and liver cancer  Rapidly converted to dieldrin in the body  bioaccumulates in fatty tissues

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