Adipocyte size and lipogenic enzyme activities in different adipose tissuedepots in steers of local Spanish breeds

The effect of genotype on the size of adipocytes and on the lipogenic enzym e activities in different fat depots in Asturiana, Avilena, Morucha, Parda Alpine, Pirenaica, Retinta and Rubia Gallega steers teas studied (six anima ls per breed). Steers were weaned at about 6 to 8 months of age and 220 to 260 kg live weight (LW). During the fattening period the steers were given commercial concentrates and straw, both ad libitum, until slaughter at 470 kg average LW. Adipocyte size and activity of the following lipogenic enzym es were studied: glycerol 3-phosphate dehydrogenase (G 3-PDH); fatty acid s ynthase (FAS); NADP-malate dehydrogenase (MD), glucose 6-phosphate dehydrog enase (G 6-PDH) and NADP-isocitrate dehydrogenase (ICDH) in the omental, pe rirenal, subcutaneous and intermuscular adipose depots. Also the perirenal fat depot teas removed and weighed and the 10th rib was dissected. Differen ces between breeds were significant for the amount of fat in the different adipose depots (P < 0.001), for adipocyte size (except in intermuscular dep ot) and for G 3-PDH, FAS, MD, ICDH (P < 0.001) and G 6-PDH (P < 0.01). In g eneral, steers of breeds that had move fat also had bigger adipocytes and h igher lipogenic enzyme activities. In this way, Asturiana breed (lean breed ) had smaller adipocytes and lower lipogenic enzyme activities than Morucha breed (fatter breed). Finally, adipocytes from the perirenal depot were th e biggest and showed the highest G 3-PDH and FAS activities while adipocyte s from the intermuscular depot had the smallest size and the lowest lipogen ic activities.