Effect of Dexamethasone on Phenylethanolamine N‐methyltransferase in Chromaffin Tissue of the Neonatal Rat

Treatment of neonatal rats with dexamethasone resulted in the appearance of phenylethanolamine‐N‐methyltransferase (PNMT) and numerous small, intensely fluorescent (SIF) cells in abdominal paraganglia and in sympathetic paravertebral ganglia. These cells may be derived from a primitive stem cell precursor, but because of their unusual anatomical features, origin from ganglion cells cannot be altogether ruled out. Associated with the proliferation of the cells was a marked increase in the PNMT activity of the tissues. The PNMT response to the glucocorticoid was limited to the first few days of life, as was the SIF cell response. After discontinuance of dexamethasone, the enzyme activity fell very rapidly, while the number of cells declined at a slower rate.