Abstract
1. The effects of mercuric acetate on glucuronide conjugation of bilirubin and 4-methylumbelliferone in vitro represent a new type of modifier of UDP-glucuronyltransferase activity.
2. Bilirubin UDPG-transferase was normally activated (optimally 4-fold), inhibition was seen only at high concn. of Hg2-. 4-Methylumbelliferone UDPG-transferase was normally inhibited by Hg2+, but at high concn. of UDPGA (10mmol/l) slight activation was seen.
3. Activation of bilirubin conjugation was unaffected by Mg 2+ concn., indicating that the mechanism of Hg2+ activation differs from that caused by Mg2+.
4. Glucuronidation of bilirubin in liver microsomes from control rats, or rats treated with phenobarbital, methylcholanthrene or TCDD respond similarly to Hg2+, confirming the view that bilirubin conjugation is not inducible by these inducers.