Distribution and metabolism of cis- and trans-resmethrin (5-benzyl-3-furyl)methyl-2,2-dimethyl 3-(2-methyl-propenyl)cyclopropanecaraboxylate in laying hens

Abstract

The cis and trans isomers of the synthetic pyrethroid, resmethrin (5-benzyl-3-furylmethyl-(IRS)-chrysanthemate), labeled with radiocarbon in either the alcohol or acid moiety, were individually administered orally to White Leghorn laying hens at a dosage of 10 mg/kg. With each isomer and label position, greater than 90% of the radiocarbon was eliminated in the excreta within 24 hours post-treatment. Radiocarbon residues in the egg white and yolk fractions were low, with peak levels observed at 1-2 and 4-5 days post-treatment in white and yolk, respectively. Residues were considerably lower in egg whites than in yolks. In birds killed 12 hours post-treatment, radiocarbon residues in tissues were low with peak levels in liver and kidney. Unmetabolized cis- or trans-resmethrin was detected in all tissues analyzed from birds killed at 12 hours post-treatment and represented the major metabolite in fat. The majority of the tissues from hens 14 days post-treatment contained no detectable levels of radiocarbon and would appear not to be indicative of appreciable residue retention. Numerous metabolites were isolated and were present in both the free and conjugated form. The metabolic routes for both resmethrin isomers arise from ester hydrolysis and oxidation of the hydrolytic products. Certain of these metabolites are further conjugated with glucuronic acid, sulfate or other unidentified compounds before excretion.