OB GENE-EXPRESSION AND SECRETION OF LEPTIN FOLLOWING DIFFERENTIATION OF RAT PREADIPOCYTES TO ADIPOCYTES IN PRIMARY CULTURE

Expression of the ob gene and production of leptin have been examined on differentiation of rat fibroblastic preadipocytes to adipocytes in primary culture. Preadipocytes were obtained from the inguinal fat pad of suckling rats, and following differentiation the cells contained l ipid droplets and the mRNAs for both lipoprotein lipase and adipsin we re detected by Northern blotting. ob mRNA was not, however, detected o n Northern blots, but analysis by RT-PCR indicated that the ob gene wa s expressed, particularly after differentiation. Measurement of leptin in the culture medium by ELISA showed that the ob gene product was se creted by adipocytes from approximately 4 days after the induction of differentiation. Leptin production was sustained over a a-week period with a peak at 8-10 days post-induction. Dexamethasone stimulated lept in production, while an inhibition was observed with the beta-adrenoce ptor agonist isoprenaline. These results demonstrate that following th e differentiation of fibroblastic preadipocytes to adipocytes in prima ry culture, leptin is secreted with the cells responding to stimuli wh ich regulate production of the hormone. (C) 1997 Academic Press