DEVELOPMENTAL-CHANGES IN APOLIPOPROTEIN-B GENE-EXPRESSION IN THE LIVER OF FETAL CALVES

Changes in apolipoprotein (apo B) gene expression in the liver were de termined in fetal calves from 90 to 260 days of intrauterine life. Res ults were compared with those obtained from the livers of I-month-old calves and adult cows. By Western blot analysis using a rabbit antiser um to bovine apo B, apo B100 was detected from 90 days of intrauterine life. Apo B100 was shown to be the only form of apo B detected in the liver of fetal calves whatever the gestational age indicating the lac k of editing process during the prenatal period. Hepatic apo B content s were stable during intrauterine life and comparable to those of calv es and lower than those of cows. Hepatic contents of apo B mRNA. incre ased with the gestational age similarly to total RNA. Values of apo B mRNA at 260 days of intrauterine life were comparable to those in the liver of 1-month-old calves and adult cows. These results suggested th at hepatic synthesis of calf apo B during fetal development is specifi cally regulated at a posttranscriptional level, either by a decrease i n the rate of translation and/or by an increase in the rate of intrace llular apo B degradation.