ONTOGENIC EXPRESSION OF DETOXICATION ENZYMES IN AN AUSTRALIAN MARSUPIAL, THE BRUSHTAIL POSSUM (TRICHOSURUS-VULPECULA)

Marsupials and eutherians display vastly different reproductive strate gies. Marsupials are characterised by the production of altricial neon ates with little functional capacity. An investigation of the ontogeni c expression of phase I (mixed function oxidase) and phase II (glutath ione transferase) enzyme systems in the marsupial, the brushtail possu m was undertaken. Enzyme expression in the youngest age group studied (60 days old) was between 5% and 10% of the adult level. A gradual inc rease in expression was then observed until a significant 3-fold incre ase to adult levels of expression of cytochrome P450, cytochrome b(5) and glutathione transferase content and ECOD and AE activity was obser ved in brushtail possum young between the ages of 150 +/- 15 and 180 /- 15 days. The expression of EROD activity reached adult levels by th e age of 150 +/- days, while the expression of NADPH cytochrome c redu ctase activity was delayed and adult levels had not yet been achieved by the oldest group studied (>200 days). The ontogenic expression of d etoxication enzymes was significantly delayed in the marsupial in comp arison to eutherians. Adult levels were achieved during the weaning pe riod, suggesting that dietary xenobiotics act as a regulatory mechanis m in the developmental expression of these enzymes in the brushtail po ssum. (C) 1997 Elsevier Science Inc.