Epidermal growth factor: a potential paracrine and autocrine system within the pituitary.

Epidermal growth factor (EGF) secretion and EGF receptor (EGFR) expression were studied by a combination of reverse hemolytic plaque assay (RHPA), which identifies the EGF secreting cells, and immunocytochemical detection of EGFR. Our results showed that 19% of total rat anterior pituitary (AP) cells secrete EGF and 48% of total AP cells possess EGFR. In addition, most of the EGF-secreting cells (73%) possess EGFR. By measuring the size of plaques surrounding EGF-secreting cells, we found that EGF secretion per cell is significantly higher in cells that did not express EGFR (1930 +/- 92 microns2) than in EGFR-expressing cells (1551 +/- 89 microns2). Taken together, these results strongly suggest that EGF acts by both an autocrine and paracrine fashion in the rat anterior pituitary gland.