Involvement of cyclic nucleotides and IP3 in the regulation of luminescence in the brittlestar Amphipholis squamata (Echinodermata)

We investigated the effects of cyclic nucleotides (cGMP, cAMP) and the phos phoinositide IP3 on the luminescence of the ophiuroid Amphipholis squamata. The cGMP analogue, dibutyryl-cGMP, and the guanylate cyclase activator, so dium nitroprusside, had no effect on the luminescence. The cAMP analogue, d ibutyryl-cAMP, and the adenylate cyclase activator, forskolin, triggered lu minescence. Moreover, the adenylate cyclase inhibitor, MDL-12330A, signific antly reduced ACh-induced luminescence. The phospholipase C inhibitor, U-73 122, also significantly reduced ACh-induced luminescence. The results sugge st that ACh-induced luminescence is mediated by both cAMP and IP3 pathways but not by cGMP. The effects of calcium-free ASW confirmed this hypothesis. A hypothetical scheme of the transduction mechanisms involved in the intra cellular control of luminescence is presented. Copyright (C) 2000 John Wile y & Sons, Ltd.