VASCULAR AND LIPOLYTIC RESPONSES TO INFUSED NOREPINEPHRINE IN CANINE SUBCUTANEOUS AND OMENTAL ADIPOSE TISSUES

Abstract

Vascular and lipolytic responses to i.v. administered norepinephrine (NE, 1 .mu.g/kg per min for 30 min) were examined in autoperfused canine subcutaneous and omental adipose tissues. In response to NE, arterial perfusion pressures increased initially and then returned gradually to the pre-infusion levels. Shortly after the onset of NE infusion, the blood flow increased greatly in both adipose tissues. The higher blood flow was maintained throughout the whole infusion period in the subcutaneous adipose tissue, whereas in the omentum the initial high flow fell gradually to the pre-infusion level. Vascular resistance started to decrease after 2-5 min from the onset of NE infusion in the subcutaneous adipose tissue and the reduction of resistance was consistent as the infusion continued. NE infusion increased the net output of FFA [free fatty acid] from the subcutaneous adipose tissue, but not in the omentum. The increased FFA output seemed to coincide with the decrease in vascular resistance. Omental adipose tissue may not be influenced by NE at the concentration tested. A marked fall in the blood flow was observed in the hindleg of the same animals, but not in the adipose tissues. There was a qualitative difference in the effects of norepinephrine on adipose tissues from different locations in the same animal. The lipolytic response occurred only if active vasodilatation was present in these tissues.