REGULATION OF GLUTAMATE-DEHYDROGENASE EXPRESSION IN THE DEVELOPING RAT-LIVER - CONTROL AT DIFFERENT LEVELS IN THE PRENATAL PERIOD

To study the regulation of the expression of glutamate dehydrogenase ( Glu-DH) in rat liver during development, the Glu-DH mRNA concentration in the liver of rats ranging in age from 14 days prenatal development to 3 months after birth was determined. This concentration increased up to two days before birth, decreased rapidly between two days before and one day after birth and increased again in the second and third p ostnatal week. The ratio of Glu-DH mRNA/protein decreased more than 10 -fold in the prenatal period, whereas it did not change significantly after birth. Thus, whereas the ratio between the Glu-DH monomer protei n molecules and Glu-DH mRNA molecules is found to be approximately 140 0 at 14 days of prenatal development, it is approximately 17000 four w eeks after birth. We argue that an increase in the translational effic iency after birth is the most likely cause of the observed development al changes in Glu-DH mRNA/protein ratio. Our results suggest that the expression after birth is predominantly regulated at the pretranslatio nal level, whereas the prenatal Glu-DH expression is regulated both at the translational level and at the pretranslational level.