Embryonic rat adrenal glands in organ culture: effects of dexamethasone, nerve growth factor and its antibodies on pheochromoblast differentiation.

In the present study we sought to determine the developmental potentialities and restrictions of adrenal medullary cells (pheochromoblasts) by investigating their morphological and biochemical response to nerve growth factor (NGF), anti-NGF antibodies and dexamethasone (DEX) after explantation into culture at different embryonic stages. With the exception of explants taken at embryonic day 15 (E 15) cultures of embryonic adrenal glands showed neurite outgrowth, which was not influenced by the addition of NGF, anti-NGF antibodies or DEX to the culture medium during the 4-day-culture period. Pheochromoblasts in E 17 + 4 explants showed spontaneous ultramorphological and biochemical maturation in terms of an increase in the number of catecholamine storage vesicles (CSVs) per micron 2 of cytoplasmic area, diameters of the cores of CSVs, percentages of electron-lucent cores of CSVs indicative of increased storage of adrenaline, overall catecholamine (CA) content and relative amount of adrenaline. NGF did not significantly affect this maturational process. Anti-NGF antibodies slightly decreased the proportion of adrenaline. The most pronounced maturation was seen in response to DEX and DEX plus NGF, although a maturational state equivalent to the E 21 stage was not achieved. E 21 + 4 explants showed neither spontaneous nor drug-induced biochemical maturation. Medullary cells in NGF-treated E 21 explants frequently retained the morphological features of pheochromoblasts. Treatment with anti-NGF antibodies significantly reduced the portion of adrenaline as compared to any other treatment. We conclude that under the culture conditions employed (1) a few pheochromoblasts spontaneously express a neuronal phenotype, (2) differentiation of pheochromoblasts towards chromaffin cells is enhanced by glucocorticoids but not by NGF, and (3) anti-NGF antibodies do not impair spontaneous neuritic growth and morphological maturation of pheochromoblasts, but cause a small reduction in the relative amount of adrenaline.