Glucocorticoid regulation of phenylethanolamine N-methyltransferase (PNMT) in organ culture of superior cervical ganglia

Glucocorticoid regulation of the adrenergic enzyme, phenylethanolamine N-methyltransferase (PNMT) was studied in organ cultures of the superior cervical ganglion (SCG) from newborn rats. Although PNMT catalytic activity was present in control ganglia, enzyme levels were too low to allow visualization of PNMT immunofluorescent cells. Addition of dexamethasone (DEX) or corticosterone to the medium resulted in a large increase in PNMT activity and bright PNMT immunoreactive (PNMT-IR) staining in cells resembling small, intensely fluorescent (SIF) cells. Addition of non-glucocorticoid steroids was ineffective. Exposure to a brief, 2-hr pulse of DEX (10^-6 M) in vitro elicited the same increase in PNMT as continual exposure to DEX. Studies using metabolic inhibitors demonstrated that the steroid-dependent increase in PNMT activity required both protein and RNA synthesis. Furthermore, the increase was inhibited by cytochalasin B and by the glucocorticoid receptor antagonists, DEX 21-mesylate and cortisol 21-mesylate. These observations suggest that glucocorticoids increase PNMT protein in SIF cells by interacting with specific steroid receptors that undergo translocation to the nucleus.