Metabolism of adipose tissue in the fat tail of the sheep in vivo.

The metabolism of the large mass of adipose tissue constituting the fat tail of the Syrian sheep has been investigated by measuring arteriovenous concentration (A-V) differences. The tail in situ in the intact anesthetized animal, as well as the isolated tail perfused with blood through a constant flow pump oxygenator, was used. In fed animals, the adipose tissue took up glucose and ketone bodies and released lactate and free fatty acids (FFA), although in some animals uptake of FFA also occurred. After 48-144 hr of fasting, uptake of glucose and ketone bodies continued and the FFA release increased. Total lipid esters and phospholipids were not released even after food had been withheld for 6 days. Insulin increased the A-V difference and the uptake of glucose, and reduced the FFA release. Adrenaline increased the A-V difference and uptake of glucose; the simultaneous increase in serum FFA was not accompanied by an increase in A-V difference for FFA in most experiments, which suggests that this adipose tissue is relatively insensitive to the lipolytic effect of the hormone. The effect of noradrenaline was similar to that of adrenaline. Glucagon hyperglycemia was not accompanied by increase in glucose uptake in most experiments.