Site-related differences in G-protein alpha subunit expression during adipogenesis in vitro: possible key role for Gq/11 alpha in the control of preadipocyte differentiation.

G protein alpha subunits were compared by immunoblotting in preadipocytes and adipocytes from rat subcutaneous and epididymal adipose tissue at three steps of adipogenesis. The most striking difference concerned the Gq/11 alpha subunits whose expression decreased during preadipocyte differentiation in subcutaneous cells while it remained constant in epididymal cells. The PKC inhibitor CGP 41251 increased glycerol 3-phosphate dehydrogenase activity (EC 1.1.1.8), a late marker of differentiation, in epididymal preadipocytes but not in subcutaneous cells. There was no difference in the proliferation capacities between subcutaneous and epididymal preadipocytes: in both cells, CGP 41251 led to the same decrease in [(3)H]thymidine incorporation and, at confluence, the amounts of Gq/11 alpha subunits were equivalent. No major site-related difference was found in the amounts of Gs and Gi alpha during adipogenesis. Thus, compared to epididymal preadipocytes, the higher capacity of subcutaneous preadipocyte to differentiate seems to be correlated with the decrease in Gq/11 alpha expression and the decreased Gq/11 mediated PKC activation.