Further studies of the metabolism of carbaryl in the rat at 30 mg per kg body weight in a single oral dose have qualitatively reproduced the chromatographic profiles from urines of rats obtained by Knaak et al. (1965) on diethylaminoethyl cellulose columns after single oral and intraperitoneal dose studies. An attempt to verify the structure of a metabolite suspected of being 1-naphthyl methylimidocarbonate 0-glucuronide (Knaak et al., 1965) has failed to confirm the hypothesis. The principal aglycone isolated from the ether-extractable fraction of an enzyme hydrolysate of this metabolite has been identified as 5,6-dihydro-5,6-dihydroxycarbaryl. When losses and unhydrolyzed glucuronide are proportioned between this aglycone and others isolated, 10.5% of the dose is excreted as the 5,6-dihydro-5,6-dihydroxycarbaryl glucuronide calculated as carbaryl equivalents.arbaryl (1 -naphthyl methylcarbamate) metabolism was first investigated by Carpenter et al. (1961). They C reported that approximately 30 % of the dose could be determined as 1 -naphthol using a colorimetric procedure. Dorough and Casida (1964) using fortified liver microsomes found hydroxylated products of carbaryl. Knaak et al. (1965) using methyl, carbonyl, and naphthyl-labeled carbaryl and diethylaminoethyl cellulose chromatography analyzed the urine of rats and guinea pigs for the conjugated metabolites and found 80 to 90 of the urinary metabolites to be anionic. In addition to the glucuronide and sulfate conjugates of 1-naphthol and 4-hydroxycarbaryl (4-hydroxy-1 -naphthyl methylcarbamate), these authors found a metabolite of carbaryl suspected of being 1-naphthyl methylimidocarbonate 0-glucuronide. A chromatographically similar metabolite was found in the urines of the monkey, pig, and sheep (Knaak et al., 1968) and possibly the dog (Knaak and Sullivan, 1967). Because this compound was excreted by a number of species, a program was undertaken to examine the nature and quantitative aspects of the metabolite.
METHODS
Chemicals.Carbaryl-methyl-' 4C (0.93 mCi per mmol) and carbaryl-1-naphthyl-' 4C (0.97 mCi per mmol) were prepared by T. E. N. Steele, Tuxedo, N. Y., as described by Knaak et al. (1965). Carbaryl-carbonyl-' 4C with a specific activity of 1.5 mCi per mmol was purchased from Volk Radiochemical Co., Chicago, Ill. The samples were shown to be 99% carbaryl-' 4C when gas chromatographed as their N-acetyl derivatives on a 5 % SE-30 column (Sullivan et al., 1967).Nonlabeled carbaryl, 5,6-dihydro-5,6-dihydroxycarbaryl, 4-and 5-hydroxycarbaryl (4-and 5-hydroxy-1-naphthyl methylcarbamate), and 1-naphthol were supplied by Union Carbide, Chemicals and Plastics Operating Division, South Charleston, W. Va. Treatment and Handling of Animals. Naphthyl-' 4C, methyl-l4C, and carbonyl-14C carbaryl (0.8, 1.4, and 0.53 pCi per mg, respectively), dissolved in polyethyleneglycol 400, were administered individually by the peroral route to groups of 12, 150-g male rats at 30 mg per kg. First-day urines were collected and pooled separately according to label. ...
