Differences in the response of UCP1 mRNA to hormonal stimulation between rat and mouse primary cultures of brown adipocytes.

UNLABELLED Uncoupling protein 1 (UCP-1), the specific marker of brown adipose tissue, is transcriptionally activated in response to adrenergic stimuli and thyroid hormones are necessary for its full expression. We describe differences in the regulation of UCP-1 mRNA expression between rat and mouse brown adipocytes in culture, using norepinephrine (NE), triiodothyronine (T3), insulin and retinoic acid (RA). RESULTS NE and cAMP-elevating agents strongly increase UCP-1 mRNA levels in cultures of mouse adipocytes, but increases are low in those from rat. In rat adipocytes NE poorly increases UCP-1 mRNA expression and T3 markedly increases the adrenergic response of UCP-1, an effect not observed in mouse adipocytes. In the absence of insulin, T3 itself increases UCP-1 mRNA in rat adipocytes and enhances the response to NE, while in mouse adipocytes no effect of T3 is observed. RA by itself stimulates UCP-1 mRNA in mouse adipocytes, but not in those from rat. In rat cultures, RA requires the presence of NE and/or T3. CONCLUSIONS We find important differences in the hormonal regulation of UCP-1 mRNA expression in cultured preadipocytes depending on the species used as donor; those differences are observed using identical culture conditions and should be considered when doing cultures from these species.