Digitoxin, a multiple spike stimulator of insulin release in the perifused islets of the rat

Summary On the basis of an analogy between stimulus-secretion coupling in the B-cell and excitation-contraction coupling in muscle, we have made the hypothesis that a cardiac glycoside Digitoxin (0.25 μM) by possible action on B-cell contractile filaments may produce insulin release. Our findings indicate that Digitoxin in the presence of 30 or 60 mg per cent glucose produces insulin release by repeated activation of the “first phase” with a pattern of secretion similar to what has been described recently to be the normal in the glucose perifused rabbit islets. This cardiac glycoside also produced a partial inhibition of glucose (300 mg per cent) induced insulin release, indicating a competitive action of these two substances. Digitoxin being the only drug reported up to the present that stimulating insulin release, partially inhibits glucose induced insulin release.