Phospholipase C isozymes are differentially distributed in the rat adrenal medulla

Immunohistochemistry has been used to examine the distribution of selected phospholipase C (PLC) isozymes within the adrenal medulla of the rat. PLCβ isozymes were expressed at moderate levels in the chromaffin cells but more strongly in association with ganglion cell clusters. PLCβ2 and PLCβ3 staining of clusters did not overlap suggesting selective PLC isozyme expression in two distinct ganglionic types. The distribution of PLCβ4 immunoreactivity was very similar to PLCβ3 with the strongest staining observed in the same cell clusters. Antibodies to PLCβ1 labelled multiple bands on Western blots and were not therefore used for immunohistochemistry. The chromaffin cells were also immunoreactive for PLCγ1, although the strongest staining with this antibody was seen in cells surrounding large sinus vessels. PLCδ1 and PLCδ2 had quite distinct distributions, with the former selectively localized to an endothelial cell population surrounding the chromaffin cells. This observation was supported by experiments on isolated bovine adrenal medullary cells where PLCδ1 expression was lost when the cell preparation was enriched for chromaffin cells. Antibodies to PLCδ2 labelled a network of nerve fibres throughout the medulla and clusters of ganglion cells located primarily at the medullary-cortical boundary. PLCδ2 immunoreactivity was also present in nerve fibres within the adrenal capsule where it appeared to be co-localized with PLCβ4 staining.