Glucocorticoid regulation of adrenomedullin in a rat model of endotoxic shock

Wistar rats were injected intravenously with bacterial lipopolysaccharide (LPS) and developed endotoxic shock with severe hypotension. This was accompanied by significantly elevated concentrations of adrenomedullin (AM) in the plasma and expression of high levels of AM mRNA in the lung. Pretreatment of the rats with dexamethasone (DEX) prevented hypotension caused by LPS administration, but plasma AM concentrations and AM mRNA levels in the lung remained elevated. Adrenalectomized (ADX) rats developed a more severe form of circulatory shock in response to a low-dose of LPS. This was accompanied by only a slight increase in circulating AM in the plasma. However, pretreatment of ADX rats with DEX caused substantial elevations of plasma AM concentrations and expression of AM mRNA in the lung. Our studies demonstrate that glucocorticoid upregulates the expression and secretion of AM in vivo, and endogenous glucocorticoid is required for increased AM secretion under certain conditions such as endotoxic shock.