Effects of splanchnic nerve stimulation on the adrenal cortex may be mediated by chromaffin cells in a paracrine manner.

The effects of nerve activation and of the catecholamines epinephrine and norepinephrine on adrenal corticosteroid release were investigated in intact isolated perfused pig adrenals with preserved nerve supply. To study the contact zones of medullary and cortical tissues, porcine adrenals were examined on the histological and ultrastructural levels. Splanchnic nerve activation stimulated in parallel the release of epinephrine (from a basal value of 0.31 +/- 0.11 to 8.13 +/- 0.60 microgram/min) and norepinephrine (from 0.76 +/- 0.68 to 12.94 +/- 3.58 micrograms/min) and the release of the corticosteroids cortisol (from 0.62 +/- 0.19 to 2.00 +/- 0.35 micrograms/min) and aldosterone (from 3.34 +/- 0.59 to 7.53 +/- 1.63 ng sigma in). Also, perfusion of the isolated adrenals with catecholamines provoked a significant release of the corticosteroids. Epinephrine (10(-6) M) stimulated the release of cortisol (from 0.59 +/- 0.31 to 2.66 +/- 0.34 micrograms/min) and aldosterone (from 2.12 +/- 0.42 to 4.68 +/- 0.92 ng/min). Norepinephrine (10(-6) M) stimulated the release of cortisol (from 0.26 +/- 0.07 to 1.28 +/- 0.10 micrograms/min) and aldosterone (from 1.28 +/- 0.37 to 3.57 +/- 0.80 ng/min). Using an immunostaining for synaptophysin, which is specific for neuroendocrine cells, chromaffin cells could be detected within all three zones of the adrenal cortex. The two endocrine tissues appear to be closely interwoven. On the ultrastructural level, medullary cells are in apposition to cortical cells, with close cellular contacts. These results show that the release of corticosteroids cortisol and aldosterone can be stimulated through the sympatho-adrenal system. Taking into consideration the close colocalization of cortical and medullary tissues, this stimulation may be mediated by chromaffin cells in a paracrine manner.