IMMUNOHISTOCHEMICAL DEMONSTRATION OF THE SYNTHESIS ENZYME FOR NITRIC-OXIDE AND OF COMEDIATORS IN NEURONS AND CHROMAFFIN CELLS OF THE HUMAN ADRENAL-MEDULLA

Within the human adrenal medulla immunoreactivity for the nitric oxide (NO)-generating enzyme nitric oxide synthase (NOS) was demonstrated i n neurons, nerve fibres and chromaffin cells. Correlation of NOS-immun oreactivity with immunostaining for the peptides neuropeptide Y, somat ostatin, substance P or vasoactive intestinal polypetide and for the c atecholamine synthesis-enzyme tyrosine hydroxylase, respectively, in n erve cell bodies revealed colocalization of NOS only with substance P. Sparse intramedullary NOS-immunoreactive varicose nerve fibres associ ated with blood vessels or with chromaffin tissue were devoid of immun oreactivities for tyrosine hydroxylase or for the investigated peptide s. Small NOS-immunolabeled cells belonged to the catecholamine-contain ing chromaffin cell population and costored VIP, but were distinct fro m the somatostatin- or neuropeptide Y- immunostained chromaffin subpop ulations. The localization of NOS in distinct structural components of the human adrenal medulla indicates that NO is produced in different cell types and may reflect a differential role of this messenger syste m in autonomic control of adrenal gland function.