Effects of insulin, glucagon, and epinephrine on the plasma membrane of the white adipose cell: a freeze-fracture study.

A quantitative study of the adipocyte plasma membrane under the influence of lipipolytic or lipogenic hormones has been carried out by freeze-fracture. The number of plasma membrane invaginations (so-called pinocytosis) and of intramembranous particles was evaluated. Under the influence of either insulin, glucogon, or epinephrine, the membrane invaginations were significantly increased with respect to control adipocytes. Insulin was shown to increase the number of intramembranous particles of the plasma membrane whereas glucagon or epinephrine had an opposite effect. These data point to a hormonal modulation of the fine-structural organization of the adipocyte plasma membrane.