Lidocaine inhibits dispersed anterior pituitary cell thyrotropin and prolactin secretion induced by thyrotropin-releasing hormone or high medium potassium.

Lidocaine at a concentration greater than or equal to 0.1 mM inhibited thyrotropin (TSH) and prolactin (PRL) secretion by perifused acutely dispersed rat adenohypophyseal cells stimulated by 10-100 microM thyrotropin-releasing hormone (TRH) or 30 mM K+. The concentration of lidocaine required for half-maximal inhibition of TSH and PRL secretion was approximately 1 and 0.5 mM, respectively. Maximal lidocaine inhibition of TRH-induced secretion was induced within 15 min and a normal response to these secretagogues returned within 20 min after removal of lidocaine from the perifusion medium. The inhibition of secretion by lidocaine may be caused by blocking depolarization of the cell membrane and depressing intracellular calcium mobilization and calcium influx across the plasma membrane.