Ca2+/calmodulin effects on cAMP response in cultured chick ciliary epithelial cells

The authors investigated the influence of the elevation of intracellular Ca2+ concentration on the production of cyclic adenosine 3',5'-monophosphate (cAMP) using cultured chick embryo ciliary epithelium (CE). We examined the effects of calcium ionophore (A23187) on cAMP production after incubation with vasoactive intestinal peptide (VIP), isoproterenol (ISO), sodium fluoride (NaF) or forskolin (FSK). A23187 had no effect on the basal cAMP level, or the NaF- and FSK-stimulated responses for cAMP level; but A23187 potentiated VIP- and ISO-stimulated cAMP responses. Calmodulin antagonist (W-7) was very effective in inhibiting the potentiating effects of A23187 on VIP and ISO-stimulated production of cAMP. Our present findings suggested that Ca2+/calmodulin may potentiate the receptor-mediated cAMP pathway through Ca2+/calmodulin-dependent protein kinase in the CE.