The response of the atrial natriuretic peptide (ANP) secreting cells from both rat atria and the apex of the ventricles to dexamethasone (DEX) was analyzed by the plaque assay. In right atrial cardiocytes, 25% of the cells secreted ANP basally; DEX treatment did not alter this percentage. However, in the left atrial secretory population, a discordance between the basal (15%) and DEX stimulated (25%) percent plaque formation was found. ANP secreting cells from the ventricular apex responded similarly to DEX exposure (26%), with 8% of the cells basally releasing the hormone. These data suggest that in both the left atria and apex of the rat ventricles, exposure to DEX recruits ANP secretory cells from a non-secreting population. Consequently, the release of ANP from these tissues would increase after glucocorticoid stimulation.