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The Electrophysiological Effects of Thyrotropin-Releasing Hormone Are Similar in Human TSH- and Prolactin-Secreting Pituitary Cells^*

Laboratoire de Neurophysiologie, CNRS UA 1200, and UFR des Sciences Pharmaceutiqu.es, Uniuersité Bordeaux II Bordeaux, France
Service de Neurochirurgie, Hôpital Pellegrin (J.G.) Bordeaux, France
Service d’Endocrinologie, Hôpital Saint-André (P.R.) Bordeaux, France

Address all correspondence and requests for reprints to: Bernard Dufy, Laboratory of Neurophysiology, CNRS UA 1200, B.P. 22, University of Bordeaux II, 146 Léo-Saignat, Bordeaux Cédex 33076, France.

We studied the electrophysiological properties of individually characterized TSH-secreting cells cultured from pituitary fragments surgically removed from three patients, two who had primary TSH-secreting adenomas and one who had chronic TSH hypersecretion (hyperplasia) secondary to primary hypothyroidism. The TSH-secreting cells were excitable and had calcium-dependent action potentials. More than 80% of the cells cultured from the two patients with TSH-secreting adenomas were spontaneously active, whereas fewer cells (20%) cultured from the hypothyroid patient were spontaneously active. TRH (50 nmol/L) induced a complex pattern of electrical changes. The initial response was transient hyperpolarization (activation of potassium conductance), followed by increased low amplitude voltage fluctuations occasionally leading to action potentials. These TRH-induced electrophysiological changes were similar to those reported in rat and human PRL-secreting adenoma cells. These results suggest that TRH may have an identical mode of action in tumoral PRL and TSH cells. In the cells from the hypothyroid patient, the initial response to TRH cells was similar, but the second phase response was greater. The findings that the cells cultured from these patients behaved differently with regard to their electrophysiological characteristics (action potentials) and responses to TRH may reflect the different clinical conditions from which they were derived.

^* This work was supported by grants from INSERM (874003), CNRS (UA 1200), and EPR (Aquitaine).

Received April 26, 1988.