The effect of GH and IGF-I on preadipocytes from Large White and Meishan pigs in primary culture.

Proliferation and differentiation of preadipocytes from 7-day-old Large White (LW) and Meishan (MS) pigs were studied in primary culture. The effects of porcine GH (pGH) and IGF-I as well as the expression of GH (GHR) and IGF-I (IGF-IR) receptors mRNA were examined. Preadipocytes were exposed to serum-supplemented and serum-free medium to determine proliferation and differentiation, respectively. Proliferation was higher in MS than in LW pigs. Treatment with pGH (2 nM) or IGF-I (10 nM) resulted in a similar decrease in proliferation in LW and MS pigs. Parameters assessing differentiation and the effects of pGH and IGF-I on differentiation did not differ between the two breeds. The percentage of differentiating cells and LPL and ME activities were markedly reduced by pGH. IGF-I did not reduce differentiation significantly. Both GHR and IGF-IR mRNA were expressed in adipose tissue, adipocytes, preadipocytes, and 6-day-cultured cells from LW and MS pigs. The similar action of pGH and IGF-I on preadipocyte proliferation and differentiation, associated with the similar expression of GHR and IGF-IR mRNA in LW and MS pigs, suggests that the GH/IGF-I axis is not impaired in MS pigs. The difference in preadipocyte proliferation observed between LW and MS pigs could account for their adiposity difference.