ENDOCRINE CONTROL OF SHEEP ADIPOSE-TISSUE FATTY-ACID SYNTHESIS - DEPOT SPECIFIC DIFFERENCES IN RESPONSE TO LACTATION

The effects of lactation and insulin, growth hormone and dexamethasone (a glucocorticoid analogue) have been assessed on the rate of fatty a cid synthesis in adipose tissue from omental (abdominal), subcutaneous and popliteal (intermuscular) depots of sheep. Adipocyte mean cell vo lume was greatest in omental tissue but the rate of fatty acid synthes is was similar in omental and subcutaneous adipose tissue in non-lacta ting ewes. Insulin increased the rate of fatty acid synthesis in tissu e from all three depots and this was antagonised by growth hormone. Th e effects of growth hormone were less in omental adipose tissue from n on-lactating sheep than in the other two depots. Lactation decreased t he rate of fatty acid synthesis in all three depots, but to a lesser e xtent in omental than the other depots. Insulin resistance was apparen t in subcutaneous and popliteal tissues from lactating ewes but not in omental tissue. Omental adipose tissue, thus differs in several aspec ts from the two carcass depots. Differences in response to hormones in omental adipose tissue were apparent in young sheep before the onset of fattening when omental adipocytes are similar in size to subcutaneo us adipocytes.