Thyrotropin-stimulated electrical excitation and its refractoriness in cultured porcine thyroid cells.

This report demonstrates TSH-stimulated electrical excitation in the thyroid and its refractoriness after exposure to TSH. TSH depolarizes the membrane potentials and causes action potentials. TSH-induced electrical activity is characterized by a latent period, rapid depolarization, action potentials (usually two spikes were observed), and then repolarization to the potential level of the silent phase. This TSH-induced electrical excitation is associated with iodide discharge. Previous exposure to TSH induces refractoriness of electrophysiological excitation and iodide discharge to further TSH stimulation.