Cell adhesion molecules (CAMs) in adrenal medulla in situ and in vitro: enhancement of chromaffin cell L1/Ng-CAM expression by NGF

Abstract

We have studied the expression of the cell adhesion molecules (CAMs) L1/Ng-CAM, N-CAM, J1/tenascin, and myelin-associated glycoprotein and their common carbohydrate L2/HNK-1 epitope in normal rat adrenal gland sections as well as in adrenal medulla cell culture with and without NGF stimulation. In situ L1/Ng-CAM was observed on the surface of some but not all chromaffin cell clusters, including their closely associated extracellular matrix (ECM). N-CAM immunoreactivity was present on all chromaffin cells and ECM. The ECM of whole medullas also expressed J1/tenascin molecules. In long-term cultures, nerve growth factor (NGF) stimulation enhanced L1/Ng-CAM, N-CAM, and Thy 1.1 immunolabeling on chromaffin cells and their processes. Process outgrowth was greater from chromaffin cell clusters containing S-100 positive Schwann cells as compared to dispersed single chromaffin cells. When long bundles of chromaffin cell fibers were present, S-100, L1/Ng-CAM, and N-CAM positive Schwann cells were always found and were grouped in distinct clusters in the intervals between the chromaffin cells. In some areas, however, after NGF stimulation some chromaffin cell process development occurred despite an apparent lack of close contact with Schwann cells. NGF-activated chromaffin cells also demonstrated neurofilament- and vimentin-like-immunoreactive filaments within cell bodies and their processes. Chromaffin cells were usually found on a layer of N-CAM and fibronectin positive fibroblasts, and often were associated with laminin-immunoreactive material. These data suggest a possible role of N-CAM and L1/Ng-CAM as well as ECM laminin in process outgrowth from chromaffin cells.