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

Abstract

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 β-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.