Distribution of [Met⁵]- and [Leu⁵]-enkephalin-, vasoactive intestinal polypeptide- and substance P-like immunoreactivities in human adrenal glands

There is recent evidence that the amine storing cells of mammalian adrenal medulla also contain bioactive peptides. In the present study we examined human adrenal glands with the immunoperoxidase-bridge method using specific antisera raised against [Met⁵]- and [Leu⁵]-enkephalin, vasoactive intestinal polypeptide hormone (VIP), and substance P. Approximately one-third of the cells in the adrenal medulla demonstrated enkephalin-like immunoreactivity. The intensity of the immunostain varied among individual cells but did not appear to correlate with amine content, as determined by the formaldehyde-induced fluorescence of catecholamines. An abundant network of varicose fibre-like structures and dots, representing preterminal and terminal nerves, demonstrated vasoactive intestinal polypeptide-like immunoreactivity and were found in close proximity to medullary gland cells. Substance P-like immunoreactivity was observed in a few fibres in the medulla and cortex. However, we could not detect cells containing vasoactive intestinal polypeptide- or substance P-like immunoreactivity in adrenal glands. p ]The present findings suggest that human adrenal medullary cells contain both [Met⁵]- and [Leu⁵]-enkephalin and are richly innervated by peptidergic nerves containing vasoactive intestinal polypeptide. These peptides may modulate the release and effects of catecholamines in the adrenal medulla. The nerves with substance P-like immunoreactivity may represent a separate peptidergic neuronal system.