Fig. 2. Effects of extraction buffer on the cAMP content of untreated ecto- and endodermal layers from Aiptasia pallida tentacles. Tentacles of sea anemones starved for 72h were individually excised, snap-frozen, stored at -80°C and later extracted in two different media. For measurement of ectodermal cAMP levels, either 1ml of ice-cold 1moll^-1 formic acid, pH2.0 (filled columns), or 1ml of ice-cold 0.05moll^-1 acetate buffer, pH5.8 (open columns), was added to each frozen tentacle. The cAMP and protein contents of the soluble, freeze-thawed ectodermal layers were assayed. For measurement of endodermal cAMP levels, the insoluble residue, consisting of intact endoderm plus mesoglea, was homogenized in 1ml of 1moll^-1 formic acid or 1ml of 0.05moll^-1 acetate buffer, pH5.8, on ice, and then assayed for cAMP and protein. Data are expressed as fmolcAMPµg^-1protein. Twenty-eight sea anemones were used. Values are means ± S.E.M. (N=2 experiments; n=17 samples).