The effects of theophylline and nifedipine on corticotropin-stimulated cortisol secretion.

The adrenal cortisol response to corticotropin appears to involve both calcium and cyclic adenosine 3',5'-monophosphate (cAMP) as intracellular mediators. In 10 healthy male volunteers, the short-term administration of theophylline, which affects both intracellular calcium and cAMP, lowered basal cortisol levels but augmented the in vivo cortisol response to short-term corticotropin stimulation. Short-term administration of nifedipine, a calcium channel antagonist, had no effect on basal or peak cortisol levels but reduced the incremental cortisol response to corticotropin. The effects of both theophylline and nifedipine, although statistically significant, were modest and of questionable clinical significance but should be considered in the interpretation of the clinical corticotropin stimulation test. They may also provide some insight into the post-receptor actions of corticotropin.