Evidence from rat liver nuclear preparations that latency of microsomal UDP-glucuronosyltransferase is associated with vesiculation.
1. Nuclear, nuclear-envelope and microsomal preparations were prepared from rat liver, and their purity and morphology monitored by electron microscopy. 2. UDP-glucuronosyltransferase activity in microsomal preparations, but not in standard nuclear or nuclear-envelope preparations, displays latency from the criterion of being enhanced ('activated') by a range of detergents or the endogenous activator UDP-N-acetyl-glucosamine. 3. Nuclear preparations resemble activated rather than native microsomal preparations in failing to transfer glucuronic acid from 4-nitrophenyl glucuronide to 2-aminophenol. 4. Electron microscopy indicates that membranes of nuclear preparations and of our standard nuclear-envelope preparations remain, as in vivo, in a cisternal arrangement, whereas those of microsomal preparations are vesiculated. 5. In nuclear-envelope preparations in which vesiculation has been encouraged, the transferase can be activated by detergents. 6. We suggest that latency of UDP-glucuronosyltransferase results from vesiculation of membranes during preparation and that the latency of the microsomal transferase is largely a preparative artefact.
D000627:Aminophenols / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology / Q000648:ultrastructure; D003902:Detergents / Q000494:pharmacology; D014453:Glucuronosyltransferase / Q000378:metabolism*; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008862:Microsomes, Liver / Q000201:enzymology / Q000648:ultrastructure; D009685:Nuclear Envelope / Q000201:enzymology / Q000648:ultrastructure; D051381:Rats; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000494:pharmacology
D000627:Aminophenols; D003902:Detergents; D014537:Uridine Diphosphate N-Acetylglucosamine; D014453:Glucuronosyltransferase