The effect of insulin, glucagon and prolactin on lipid synthesis and related metabolic activity in migratory and non-migratory finches

Abstract

1. 1. The effects of insulin, glucagon and prolactin on lipid synthesis were investigated in house sparrows ( Passer domesticus) and white-crowned sparrows ( Zonotrichia leucophrys gambelii). 2. 2. The incorporation of glucose-U-C 14 and acetate-1-C 14 into abdominal fat pad lipid was measured in in vitro and in vivo experiments. 3. 3. None of these hormones accelerated lipid synthesis, even though lipogenesis is sensitive to changes in carbohydrate metabolism (i.e. glucose uptake) in this tissue. 4. 4. Insulin, a potent stimulator of lipid synthesis in mammalian adipose tissue, had no effect on the metabolism of finch fat pads. 5. 5. Glucagon and prolactin inhibited the synthesis of fatty acids from acetate. Only glucagon has the necessary potency to be of physiological significance. 6. 6. It is hypothesized that a relatively high glucagon output inhibits lipid synthesis during non-migratory periods. During migratory periods the output of glucagon falls, allowing lipid synthesis to proceed at a more rapid rate.