Membrane-bound pyroglutamyl-arylamidase activity during the first postnatal month in several rat brain areas.

Membrane-bound pyroglutamyl-aminopeptidase activity cleaves the pyoglutamate amino acid bond of thyroliberin (TRH). Information concerning developmental variations in TRH has been reported. However, little is known about the ontogeny of the membrane-bound enzyme activities capable of hydrolyzing the mentioned tripeptide. In this work we have described decreases in membrane-bound pyroglutamyl-aminopeptidase (arylamidase) activity, from day 9 to day 20 after birth, in the hypothalamus, the striatum, the frontal, occipital and parieto-temporal cortices and the pituitary gland of the male and the female rat. The developmental profile is similar in rats of both sexes. We have not found significative changes between 20 and 25 postnatal days. The observed decreasing activity is developmentally coincident with the increases in thyroliberin and decreases in Hys-Pro diketopiperazine concentration in different brain areas. It is suggested that membrane-bound pyroglutamyl-peptidase activity could play a part in the normal development of thyroliberin physiology.