Abstract:A cells culture system of rat primary preadipocytes was established in vitro to investigate the regulation of docosahexaenoic acid(DHA) on preadipocytes cycle and cyclooxygenases-2(COX-2 ), mRNA expression by treated preadipocytes (cultured day 1) and adipocytes (differentiated day 1) with 0 μmol/L (control group), 40 μmol/L (lower dose group) and 160 μmol /L (higher dose group) DHA. Preadipocytes cycles were analyzed by flow cytometry(FCM), and the expression of (COX-2 ) mRNA in adipocytes were detected by reverse transcriptase -polymerase chain reaction (RT-PCR). It was demonstrated that the percent of preadipocytes in G1 phase were increased after treated by DHA at 48 h, but no remarkable difference compared with control. Expression of COX-2 mRNA were markedly decreased after treated with 40 μmol/L DHA at 24 h, but increased in 160 μmol/L group. It can be concluded that DHA had no obvious effect on preadipocytes cycle but regulated the expression of COX-2 mRNA in a concentration-dependent manner.