In vitro effects of endogenous opiate peptides on thyrotropin function: inhibition of thyrotropin-releasing hormone release and absence of effect on thyrotropin release.
Thyrotropin-releasing hormone (TRH) or thyroid-stimulating hormone (TSH) was measured by radioimmunoassay in the incubation medium of rat hypothalami or anterior pituitary halves, respectively. We studied the effect of opioid peptide addition (10(-8) to 10(-6) M) on TRH or TSH release. alpha- or beta-Endorphin decreased TRH release in a dose-dependent manner while only 10(-6) M Leu- or Met-enkephalin decreased TRH release. These inhibitory effects were prevented by addition of naloxone (10(-5) M). In the dose range used none of the opioid peptides modified TSH release. These results indicate that opioid peptides may play a role in the regulation of thyrotropin secretion via a hypothalamic action on TRH release.
D000818:Animals; D004723:Endorphins / Q000494:pharmacology*; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D018822:alpha-Endorphin; D001615:beta-Endorphin
D004723:Endorphins; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; D018822:alpha-Endorphin; D013972:Thyrotropin