title: Direct pituitary stimulation of thyrotropin secretion by opioid peptides.
abstract: We have studied the effects of opioid peptides in vitro on the release of TSH from superfused anterior pituitary tissue. The opioid peptide beta-endorphin was found to increase TSH secretion in a dose-related manner from either dispersed pituitary cells or pituitary fragments. This effect of beta-endorphin was not blocked by a wide range of doses (10(-9)-10(-5) M) of naloxone. In contrast, somatostatin (10(-9) M) significantly decreased beta-endorphin-stimulated TSH secretion. In addition to beta-endorphin, the opioid peptides met-enkephalin, leu-enkephalin, dynorphin, and gamma-endorphin all increased, whereas des-Tyr-gamma-endorphin did not affect, TSH secretion. These results indicate that the opioid peptides may participate in the regulation of TSH secretion via a direct pituitary action.
mesh_terms: D000818:Animals; D004399:Dynorphins; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013329:Structure-Activity Relationship; D013972:Thyrotropin / Q000378:metabolism*
chemical_list: D004723:Endorphins; D004745:Enkephalins; D009294:Narcotics; D010446:Peptide Fragments; D009270:Naloxone; C026843:dynorphin (1-13); D004399:Dynorphins; D013972:Thyrotropin