Adenohypophyseal degradation of thyrotropin releasing hormone regulated by thyroid hormones.
Thyrotropin Releasing Hormone (TRH; pyroGlu-His-Pro-NH2) is important in the regulation of adenohypophyseal hormone secretion and also serves neurotropic functions in extra-hypothalamic brain areas, indicating that it is involved in neurotransmission and other forms of cellular communication. This hypothesis is strengthened by the observation that TRH is hydrolysed at the pyroGlu-His bond by a particulate enzyme located in the synaptosomal and adenohypophyseal plasma membrane. Furthermore, this enzyme has been identified as a heterogeneously distributed ectoenzyme which has a high degree of substrate specificity like the TRH-degrading serum enzyme studied previously. In the rat, the activity of the TRH-degrading serum enzyme has been shown to be influenced by the thyroid status of the animals; here I report that the activity of the membrane-bound TRH-degrading enzyme of the anterior pituitary is stringently controlled by thyroid hormones, but that the activity of the brain enzyme is not.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D007037:Hypothyroidism / Q000139:chemically induced / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011441:Propylthiouracil / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology*; D014316:Tritium
D014284:Triiodothyronine; D014316:Tritium; D013973:Thyrotropin-Releasing Hormone; D011441:Propylthiouracil