Stimulating effect of calcium channel activator BAY-K 8644 on calcitonin secretion.

The calcium channel activator BAY-K 8644 injected intravenously produces a significant rise in the calcitonin content of the thyroid. Because adrenalin and noradrenaline play a certain role in the regulation of ionic calcium channels and in the preservation of the secretory tonus of the calcitonin secreting C cells, the effect of BAY-K 8644 was followed-up in adrenalectomized animals and in animals in which propranolol was previously administered. Adrenalectomy of beta receptor blocking does not prevent the effect of BAY-K 8644 on the activation of calcium channels, the calcitonin secretion being stimulated in these conditions too. The data obtained stress the relative independence of the calcium channels or the beta-adrenergic stimulating system in the achievement of calcium ion transfer. However, the calcitonin levels obtained were lower in adrenalectomized animals or following propranolol after stimulation with BAY-K 8644 in those with intact sympatho-adrenergic tonus. This stresses the importance of the integrity of the beta receptors in the activation of the calcium channels.