Enzymic formation of TRH-OH from TRH by rat hypothalamus.
Specific radioimmunoassays for thyrotrophin-releasing hormone (TRH) and deamido-TRH (TRH-OH) were used to investigate the inactivation of TRH by subcellular fractions from rat hypothalamus. TRH-OH was rapidly formed from TRH by an amidase present only in the supernatant fraction at an optimum pH of 7.38; although TRH was degraded by the particulate fraction, no TRH-OH formation was detected. Of several brain areas investigated, the cortex had the highest rate of TRH-OH production and the pituitary the lowest. Once formed in the supernatant fractions, it was found that TRH-OH was stable and did not undergo further degradation. Formation of TRH-OH from TRH appears to be an important step in the tripeptide's enzymic degradation in the brain, so the combined use of specific radioimmunoassays for TRH and TRH-OH may provide a suitable means for studies of the enzymes involved, since these enzymes may contribute to the mechanisms regulating the secretion and duration of action of TRH.
D000581:Amidohydrolases / Q000378:metabolism*; D000818:Animals; D002474:Cell-Free System; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007031:Hypothalamus / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D011863:Radioimmunoassay; D051381:Rats; D013788:Thalamus / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000378:metabolism*
C020271:thyrotropin-releasing hormone, deamido-; D013973:Thyrotropin-Releasing Hormone; D000581:Amidohydrolases; D011761:Pyrrolidonecarboxylic Acid