Intracellular sorting of lysosomal beta-glucuronidase is altered due to administration of dibutyl phosphate.
Organophosphate compounds are known to cause a selective increase of beta-glucuronidase activity in rat serum. Previous data suggested that increase of serum beta-glucuronidase activity was well correlated with decrease of that activity in rat liver microsomal fraction, thereby, suggesting a role of the microsomal enzyme in mediating the organophosphate effect. To investigate further the intracellular sorting pathway of beta-glucuronidase in dibutyl phosphate-treated rats, liver subcellular fractions were prepared at 12 or 48 h after in vivo administration of [3H]leucine and it was established that microsomal beta-glucuronidase was the origin of the increased serum enzyme. To characterize the intracellular secretory pathway of beta-glucuronidase in dibutyl phosphate-treated rats, Golgi subfractions were isolated and a time course study was carried out. At 30 min after administration of dibutyl phosphate, specific activity of beta-glucuronidase in GF-2 (Golgi intermediate fraction) and GF-3 (Golgi heavy fraction) was significantly increased to the maximum. Furthermore, colchicine pretreatment of rats caused a delay of the peak of specific activity for 30 min in GF-2 and GF-3, and accumulation of enzyme activity in Golgi subfractions was observed. Colchicine pretreatment also had an inhibitory effect on release of beta-glucuronidase into serum until 30 min after dibutyl phosphate injection. The electrophoretic pattern of microsomal beta-glucuronidase on polyacrylamide gel was found to show two major bands of microsomal enzyme type and lysosomal enzyme type in dibutyl phosphate-treated rats. Taken together, these findings indicate that microsomal beta-glucuronidase follows the intracellular secretory pathway and is secreted into serum via Golgi complex in response to dibutyl phosphate.
Division of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka.
Y
Y
Nishimura
K
K
Kato
K
K
Oda
T
T
Ishikawa
Y
Y
Ikehara
M
M
Himeno
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D005700:Galactosyltransferases / Q000187:drug effects; D005966:Glucuronidase / Q000187:drug effects*; D006056:Golgi Apparatus / Q000187:drug effects; D008247:Lysosomes / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D010755:Organophosphates / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012636:Secretory Rate / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology
D010755:Organophosphates; C065087:di-n-butylphosphoric acid; D005700:Galactosyltransferases; D005966:Glucuronidase; D003078:Colchicine