Calcium-antagonists, or calcium-agonists can act both on the excitation-contraction coupling of arterial wall, and on the stimulus-secretion coupling of endocrine-cells. It is proposed that doses of such drugs able to act on one coupling are not of the same magnitude than those required for the other one. Evidences are proposed from studies with dihydropyridines on renin secretion and renal vasodilation of isolated perfused rat kidneys, and from studies on insulin secretion and vascular dilation of isolated perfused pancreases.