Ontogeny of hepatic microsomal 3-hydroxylation of quinine in Adélie Penguins

Abstract

Ontogeny of hepatic cytochrome P450 (CYP) content and of quinine 3-hydroxylation, a biomarker of human CYP3A activity, was investigated in Adélie Penguins ( Pygoscelis adeliae) by comparing liver microsomes from chicks aged 13–28 days ( n=10) with those from adults. The total CYP content in chick microsomes was significantly lower than in adults and correlated with the age of the chicks ( r=0.894, P<0.001). Kinetic parameters (mean±S.D.) for quinine 3-hydroxylation in chick microsomes were lower than the corresponding values in adult penguins ( K m, 122±27 vs. 160±73 μM; V max, 119±35 vs. 160±72 pmol/min/mg protein) but the differences were not significant, and neither K m nor V max correlated with age of the chicks. The pattern of inhibition of quinine 3-hydroxylation by specific human CYP inhibitors suggests that the CYP enzyme mediating quinine 3-hydroxylation in penguin chicks is similar to human CYP3A, but is a different isoform from that in adult penguins. The results imply that Adélie Penguin chicks may have a different susceptibility to environmental pollutants from adult penguins.