Effect of lactation on the metabolism of sheep adipose tissue.

The rates of incorporation of 14C glucose and 14C acetate into triglycerides by slices of omental adipose tissue were much lower in tissues from sheep in early lactation than in tissues from dry, non-pregnant sheep. The rates of oxidation of both substrates were also much lower in early lactation but increased again in late lactation. There was an increase in the incorporation of 14C acetate into triglycerides in late lactation and a further increase after the lambs were weaned. Lipoprotein lipase activity was lower in omental adipose tissue from lactating sheep than in tissue from dry, non-pregnant sheep. There were marked increases in the concentrations of nonesterified fatty acids in plasma and in adipose tissue during early lactation. The rate of release of glycerol by adipocytes in vitro also increased during lactation. These results suggest that there was a change from lipid deposition to lipid mobilisation during lactation.