Effect of insulin on cyclic nucleotide levels and promotion of mitosis by insulin and ionophore A23187 in cultured newt blastemata.

The levels of cyclic GMP (cGMP) and cyclic AMP (cAMP) were assayed, using radioimmunoassay, in newt blastemata cultured with and without insulin. Our observations show that insulin significantly increases the levels of cGMP over the control values, whereas the levels of cAMP remain unaltered. Our in vitro studies also show that Ca2+-carrying ionophore A23187, albeit capable of promoting blastema cell proliferation, is unable to replace the insulin effect. The possible role of cGMP and Ca2+ as mediators of insulin action in regeneration is discussed.