Increased expression and activity of ornithine decarboxylase in chicks genetically selected for rapid growth rate

Polyamines are essential requirements for cell proliferation and their role in stimulation of RNA, DNA, and protein synthesis is clearly established. Ornithine decarboxylase is a key enzyme in the biosynthesis of the polyamines and its activity is regulated in response to factors that stimulate cell proliferation. Steady-state ODC mRNA levels and enzyme activity were measured in muscle of chicks genetically selected for increased growth rate or for egg production. In muscle, muscle satellite cells and myotubes, two ODC mRNA transcripts are present of molecular size 2.05 and 1.75 kb. Northern blotting analysis suggest that these transcripts are produced as a result of using different polyadenylation sites. Between day 1 and day 6 after hatching, a period of rapid muscle growth in these animals, a peak in muscle ODC mRNA levels is followed by a peak in enzyme activity in both lines. Significantly higher ODC mRNA levels and enzyme activity are associated with selection for rapid growth in the broiler line. The results are consistent with other data showing that ODC is a major factor in cell growth and provide further evidence that it is a candidate 'trait-gene' for growth.