EXPRESSION OF C-ERBA-ALPHA, C-ERBA-BETA AND REV-ERBA-ALPHA MESSENGER-RNA DURING THE CONVERSION OF BROWN ADIPOSE-TISSUE INTO WHITE ADIPOSE-TISSUE

The levels of mRNA encoding uncoupling protein (UCP), thyroid hormone receptors (c-erbA alpha, c-erbA beta) and a related protein Rev-erbA a lpha have been studied in brown (pericervical) and white (perirenal) r abbit adipose tissues from birth to 180 days. The c-erbA alpha and c-e rbA beta genes are expressed at similar levels in the two tissues. The alpha 1, alpha 2 and beta 1 transcripts do not change notably during development or during the conversion From brown to white phenotype whi ch occurs in pericervical during postnatal life. Rev-erbA alpha mRNA i s barely detectable at birth and dramatically increases between 7 and 30 days. However, this increase is not tissue-specific and is also obs erved in liver and heart. In conclusion, our results show that the dec line in UCP expression during the transition from brown to white pheno type cannot be related to changes in the profiles of thyroid hormone r eceptors or Rev-erbA alpha mRNA expression. These profiles are not dif ferent between adipose tissue sites which are brown or white at birth.