Vasoactive intestinal peptide (VIP) stimulates [Ca2+]i and cyclic AMPin CHO cells expressing Galpha16.

The stimulatory effect of vasoactive intestinal peptide (VIP) and analogues on [Ca2+]i has been investigated in chinese hamster ovary (CHO) cells stably transfected with the reporter gene aequorin, and expressing either the human VPAC1or VPAC2 receptor in absence or in presence of the Galpha16. In cells that were not transfected with Galpha16 and expressed a similar density of receptors, the VIP induced [Ca2+]i ncrease was higher in VPAC1 than in VPAC2 receptor expressing cells. In aequorin/Galpha16 cotransfected cells, the VIP-induced response was higher, reaching 70 to 80% of the maximal calcium response, obtained after digitonin treatment, in response to both VPAC1 and VPAC2 receptor stimulation. The results suggest that in hematopoietic cells, which express both VIP receptors and Galpha16, the signalling pathway of VIP could be mediated through both cyclic AMP and [Ca2+]i increase.