TY - JOUR
T1 - Role of n-ghicuronidation in benzidine-induced bladder cancer in dog
AU - Babu, Satram R.
AU - Lakshmi, Vijaya M.
AU - Hsu, F. F.
AU - Zenser, Terry V.
AU - Davis, Bernard B.
N1 - Funding Information:
The authors thank Priscilla Crews for excellent technical assistance. This work was supported by the Department of Veterans Affairs (T.V.Z..B.B.D.). LC-MS was performed at Washington University, St Louis, MO in the Biomedical Mass Spectrometry Resource Center through NIH grants RR-00954 and AM-20579.
PY - 1992/7
Y1 - 1992/7
N2 - The mechanism by which benzidine induces bladder cancer in dog was evaluated by assessing me tabolism of [3H]benzidine by dog liver slices and microsomes. Slices incubated with 0.05 mM [3H]benzidine exhibited a 32.5 min peak, which was also produced when microsomal incubations were supplemented with UDP-glucuronic acid. In contrast to microsomes, very little of the 32.5 min peak was produced with the 100 000 g supernatant fraction. Microsomal metabolism was increased 5-fold by pretreatment with Triton X-100. Very little activity was observed with rat microsomes in either the presence or absence of Triton X-100. This metabolite was also generated by incubating benzidine with glucuronk add at 4°C for 3 days. Thermospray MS identified this metabolite as benzidine N-glucuronide. At 37°C, the t2-Jan stability of purified N-glucuronide was 99, 25 and 3 min in dog urine adjusted to pH 7.3, 6.3 and 5.3 respectively. The N-glucuronide was quite stable at pH 9.3, in dog plasma, and in aprotic solvents for 4 h at 37°C. Relative to benzidine, its N-glucuronide is weakly bound to plasma proteins but not more reactive with DNA. Thus, detoxification by liver provides a mechanism for accumulation of benzidine in acidic urine, uptake of benzidine into bladder epithelium, and activation of benzidine in bladder. The liver and N-glucuronidation play a potentially important role in the species specificity of benzidine carcinogenesis.
AB - The mechanism by which benzidine induces bladder cancer in dog was evaluated by assessing me tabolism of [3H]benzidine by dog liver slices and microsomes. Slices incubated with 0.05 mM [3H]benzidine exhibited a 32.5 min peak, which was also produced when microsomal incubations were supplemented with UDP-glucuronic acid. In contrast to microsomes, very little of the 32.5 min peak was produced with the 100 000 g supernatant fraction. Microsomal metabolism was increased 5-fold by pretreatment with Triton X-100. Very little activity was observed with rat microsomes in either the presence or absence of Triton X-100. This metabolite was also generated by incubating benzidine with glucuronk add at 4°C for 3 days. Thermospray MS identified this metabolite as benzidine N-glucuronide. At 37°C, the t2-Jan stability of purified N-glucuronide was 99, 25 and 3 min in dog urine adjusted to pH 7.3, 6.3 and 5.3 respectively. The N-glucuronide was quite stable at pH 9.3, in dog plasma, and in aprotic solvents for 4 h at 37°C. Relative to benzidine, its N-glucuronide is weakly bound to plasma proteins but not more reactive with DNA. Thus, detoxification by liver provides a mechanism for accumulation of benzidine in acidic urine, uptake of benzidine into bladder epithelium, and activation of benzidine in bladder. The liver and N-glucuronidation play a potentially important role in the species specificity of benzidine carcinogenesis.
UR - http://www.scopus.com/inward/record.url?scp=0026637260&partnerID=8YFLogxK
U2 - 10.1093/carcin/13.7.1235
DO - 10.1093/carcin/13.7.1235
M3 - Comment/debate
C2 - 1638692
AN - SCOPUS:0026637260
SN - 0143-3334
VL - 13
SP - 1235
EP - 1240
JO - Carcinogenesis
JF - Carcinogenesis
IS - 7
ER -