Adrenergic Innervation of Fetal Pig Adipose Tissue

Histochemistry and electron microscopy were used to study the adrenergic innervation of subcutaneous adipose tissue in fetal pigs. Adrenergic innervation was present around arteries, arterioles, and adipocyte-associated capillaries. Nerve fibers were infrequently observed around veins, venules, and adipocytes. Ultrastructural features of nerves included mitochondria, clear synaptic vesicles, and a small number of vesicles with a core of electron-dense material. Innervation of adipose tissue was similar in 70-, 90-, and 110-day-old fetuses. Examination of fetuses decapitated at 45 days of gestation and removed at 110 days showed that adrenergic innervation was absent in adipose tissue of decapitated fetuses. Adrenergic innervation was also absent in adipose tissue from fetuses hypophysectomized at 72–73 days of gestation and examined at 110 days. These data indicate that fetal porcine adipose tissue may be under neural control by day 70 of gestation. Furthermore, an intact pituitary is necessary for the development of adrenergic innervation in fetal adipose tissue.