Development of Liver Microsomal Oxidations in the Chick

Abstract

1. Liver microsomal preparations from chick embryos (1 day before hatching) and from 1-7 day old chicks were assayed for oxidative drug-metabolizing activity with aminopyrine, aniline and naphthalene as substrates. 2. Activities for all three substrates were highest in preparations from 1 day-old chicks. These were more than twice as active as the 7 day-old preparations and about three times as active as those from the embryos. 3. The increase in drug-metabolizing activities in newly-hatched chicks was the same for either sex and persisted for 3 days before declining towards the 7 day-old levels. 4. The developmental time-course fo the liver microsomal drug-metabolizing activities was independent of any factor in the 105 000 g supernatant fractions and of such microsomal parameters as cytochrome b5 and cytochrome P-450 content, and NADPH-cytochrome c reductase activity, but was related to changes in NADPH-cytochrome P-450 reductase levels. 5. Treatment of 7 day-old chicks with exogenous inducers, 3-methylcholanthrene or phenobarbital sodium (100 mg/kg, intraperitoneally) brought about maximal stimulation of microsomal activity as 18-24 h. The time-course of this induction was reflected by changes in microsomal cytochrome P-450 content and NADPH-cytochrome P=450 reductase activities. 6. Some induction of liver microsomal drug metabolism in 7 day-old chicks could also be brought about by injecting certain lipid-soluble egg yolk extracts.

Development of basal and induced aryl hydrocarbon (benzo[a]pyrene) hydroxylase activity in the chicken embryo in ovo.

“…It was later reported that newly hatched chickens had 3-4 times the adult enzyme activity and that this remained high for several days before returning to adult levels (8). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was first shown to be a potent inducer of 8-aminolevulinic acid synthetase and aryl hydrocarbon hydroxylase (AHHase; designated elsewhere as AHH) activity in the 17-DI chicken embryo (9).…”

Xenobiotic monooxygenase activity and the response to inducers of cytochrome P-450 during embryonic and larval development in fish

“…adult trout (Table 5-1). The ontogeny of BPM activity in brook trout resembles that seen in chicken, where bùbstantial monooxygenase activity is present before hatching, and within 1 day after hatching activity rises to about twice the adult level (Powis et al, 1976).…”

“…Another possibility is that changes in the functional association of cytochrome P-450 and its reductase are responsible for the increased BPM activity after hatching. As discussed in the introduction, in the livers of chickens there is about a 3-fold increase in certain microsomal monooxygenase activities within 24 hours of hatching, but little change in the content of cytochrome P-450 or the level of NADPH-cytochrome c reductase activity (Powis et al, 1976).…”

“…Cresteil et ~., 1979;DaUner et ~., 1966;Gielen et ~., 1972;Lucier et al, 1975;Manchester and Neims, 1977;Rane et !l., 1973). Increases in hepatic monooxygenase ac tivi ties short ly after hatching also occur in chickens (Powis ~ al., 1976). The Fundulus data are not directly comparable to the mammalian or avian liver data, since preparations from whole embryos were used.…”

“…Apparent ly the only nonmammalian species in which the ontogeny of the microsomal monooxygenase system has been examined is the chicken (Drummond et ~., 1972;Powis et al, 1976;Rifkind et ! !., 1979 values; within one day of hatching they peaked at 3-fold higher levels, then gradually fell off to the adult levels within 7 days.…”