Role of naloxone and opioid peptides on thyrotrophin, alpha subunit and beta thyrotrophin by dispersed rat pituitary cells.
This study was undertaken to determine the effect of opioid peptides and naloxone on the secretion of thyrotrophin (TSH), alpha subunit (alpha subunit) and beta thyrotrophin (TSH-beta) from rat pituitary dispersed cells in primary culture. Naloxone (NAL) 10(-5) M was found to increase basal TSH, alpha subunit and TSH-beta secretion. This effect of NAL was not blocked by human beta-endorphin (beta h-End) 10(-7) M. Concurrent treatment with triiodothyronine (T3) 10(-7) M significantly decreased NAL stimulated secretion of TSH and its subunits. Thyrotrophin releasing hormone (TRH) stimulation of secretion of TSH and its subunits was not further augmented by NAL. In contrast, 10(-7) M of beta h-End, methionine-enkephalin (Met-Enk) and D-ala2-met-enkephalinamide (DALA) had no effect on secretion of TSH and subunits. A time course study confirmed no change in TSH secretion following pre-treatment with beta h-End at 4, 10, 24 and 48 h. These findings go against a direct action of beta h-End, Met-Enk and DALA on TSH secretion. The response of TSH and its subunits to NAL and the lack of interaction with beta h-End might be explained by the existence of different types of opiate receptors. Counteraction of this effect by T3 suggests other possible mechanisms.
Cacicedo
L
L
Sánchez Franco
F
F
D000818:Animals; D002478:Cells, Cultured; D004723:Endorphins / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D015292:Glycoprotein Hormones, alpha Subunit; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology; D001615:beta-Endorphin
D004723:Endorphins; D015292:Glycoprotein Hormones, alpha Subunit; D010446:Peptide Fragments; D010908:Pituitary Hormones, Anterior; D011957:Receptors, Opioid; D014284:Triiodothyronine; D009270:Naloxone; D004744:Enkephalin, Methionine; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; C022118:enkephalinamide-Met, Ala(2)-; D013972:Thyrotropin