Evidence for the absence of cysteine S-conjugate N-acetyltransferase activity in the metabolism of propachlor, naphthalene, and dichlobanil in calves.

1. The glutathione conjugate of 2-chloro-N-isopropyl[1-14C]acetanilide (14C-propachlor) was perfused through a calf kidney in situ; 23% of the dose was excreted in the perfused kidney urine as the cysteine conjugate, no mercapturic acid was detected. 2. A 5-day-old calf dosed orally with 14C-propachlor excreted 70% dose in the urine as the cysteine conjugate; no mercapturic acid was detected. Rumen microflora were established in the calf (5 weeks older) and the experiment was repeated with the same results. 3. When the same calf was dosed 1 week later with 14C-naphthalene, 99% dose was excreted in the urine, mostly as the dihydrodiol-glucuronide (34%) and the dihydrohydroxy-cysteine conjugate (47%); no mercapturate was detected. 4. A 9-day-old calf dosed orally with 2,6,-dichlorobenzo[14C]nitrile (14C-dichlobanil) excreted 67% dose in the urine as cysteine conjugates (34%), and products of cysteine conjugate beta-lyase cleavage of cysteine conjugates (30%); no mercapturates were detected. 5. Cysteine S-conjugate N-acetyltransferase activity in calf kidney and liver was about 10% of that in the corresponding rat tissues.