AJP - Endocrinology and Metabolism, Vol 241, Issue 4 298-E304, Copyright © 1981 by American Physiological Society
Action of thyrotropin-releasing hormone on mammotrophs and thyrotrophs
G. Snyder, Z. Naor, C. P. Fawcett and S. M. McCann
Anterior pituitary cells from 15-day female rats were separated by unit
gravity sedimentation into four populations (designated regions I-IV) based
on the profile of cell distribution and the resulting content of
radioimmunoassayable (RIA) hormones. The cells in regions II and IV
released thyrotropin (TSH) in response to thyrotropin-releasing hormone
(TRH, 5 ng/ml); however, those in region IV released only approximately 5%
of their RIA content, whereas those in region II released approximately 26%
in response to the same stimulus. Concomitant elevation of cAMP and of cGMP
occurred in region II cells but only cGMP was elevated in region IV cells.
Mammotrophs were localized in region III. They responded to TRH by
releasing prolactin (PRL) and exhibiting increased cAMP content. These data
provide support for the existence of two functionally distinct populations
of thyrotrophs in 15-day-old female rats. The data also imply that cAMP is
involved in TRH induced PRL release, whereas cGMP is involved in
TRH-induced TSH release.
