Nitric oxide inhibition of cAMP synthesis in parotid acini: regulation of type 5/6 adenylyl cyclase

The nitric oxide (NO) donor, GEA 3162, inhibited isoproterenol-induced cyclic AMP (cAMP) accumulation in a concentration- and time-dependent manner in mouse parotid acini; SIN-1 mimicked these effects. Inhibition of stimulated cAMP accumulation was independent of phosphodiesterase activity. GEA 3162 also inhibited forskolin-induced cAMP accumulation. Removal of extracellular Ca(2+), addition of La(3+), or the calmodulin (CaM) inhibitor, calmidazolium, did not prevent the NO-mediated response, and addition of the soluble guanylyl inhibitor, ODQ, did not reverse GEA 3162-induced inhibition of cAMP accumulation. GEA 3162 also inhibited adenylyl cyclase in vitro independently of Ca(2+)/CaM. Further studies revealed that the NO synthase (NOS) inhibitor, 7-nitroindazole (7-NI), reduced significantly thapsigargin-induced Ca(2+) release and capacitative Ca(2+) entry and reversed thapsigargin inhibition of the AC Type 5/6 isoform (AC5/6). Data suggest that NO produced endogenously has dual effects on cAMP accumulation in mouse parotid acini, an inhibitory effect on AC activity and a modulatory effect on capacitative Ca(2+) entry resulting in AC5/6 inhibition.