Effects of opioid peptides on thyrotropin-releasing hormone release from the rat caecum in vitro.
Effects of opioid peptides (beta-endorphin, dynorphin (1-13). alpha-neoendorphin, beta-neoendorphin, leucine-enkephalin, methionine-enkephalin) on the release of thyrotropin-releasing hormone (TRH) from the rat caecum were studied in vitro. The rat caecum was incubated in medium 199 with 1.0 mg/ml of bacitracin (pH 7.4) (medium). The amount of TRH release from the rat caecum into the medium was measured by radioimmunoassay. The immunoreactive TRH (ir-TRH) release from the rat caecum was inhibited significantly in a dose-related manner with the addition of opioid peptides. The inhibitory effects of opioid peptides on ir-TRH release from the rat caecum were blocked with an addition of naloxone. The elution profile of acid-methanol-extracts of rat caecum on Sephadex G-10 was identical to that of synthetic TRH. The findings suggest that opioid peptides inhibit TRH release from the rat caecum in vitro.
Mitsuma
T
T
Fourth Department of Internal Medicine, Aichi Medical University, Japan.
Hirooka
Y
Y
Nakata
K
K
Nogimori
T
T
D000818:Animals; D002432:Cecum / Q000378:metabolism*; D004723:Endorphins / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D004723:Endorphins; D013973:Thyrotropin-Releasing Hormone