Further studies on the regulation, localization and function of the TRH-like peptide pyroglutamyl-glutamyl-prolineamide in the rat anterior pituitary gland.
Recent evidence shows that thyrotrophin-releasing hormone (TRH) immunoreactivity in the rat anterior pituitary gland is accounted for by the TRH-like tripeptide pyroglutamyl-glutamyl-prolineamide (pGlu-Glu-ProNH2, < EEP-NH2). The present study was undertaken to investigate further the regulation, localization and possible intrapituitary function of < EEP-NH2. Anterior pituitary levels of < EEP-NH2 were determined between days 5 and 35 of life, during the oestrous cycle and after treatment with the luteinizing hormone-releasing hormone (LHRH) antagonist Org 30276. Treatment of adult males with the LHRH antagonist either for 1 day (500 micrograms/100 g body weight) or for 5 days (50 micrograms/100 g body weight) reduced anterior pituitary < EEP-NH2 levels by 25-30% (P < 0.05 versus saline-treated controls). Anterior pituitary < EEP-NH2 increased between days 5 and 35 of life. In females, these levels were 2- to 3-fold higher (P < 0.05) than in males between days 15 and 25 after birth; these changes corresponded with the higher plasma follicle-stimulating hormone (FSH) levels in the female rats. After day 25, < EEP-NH2 levels in female rats decreased in parallel with a decrease in plasma FSH. Injections with the LHRH antagonist (500 micrograms/100 g body weight), starting on day 22 of life, led to reduced contents of < EEP-NH2 in the anterior pituitary gland of female rats on days 26 and 30 (55 and 35% decrease respectively). Levels of < EEP-NH2 in the anterior pituitary gland did not change significantly during the oestrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)
Rondeel
J M
JM
Department of Endocrinology and Reproduction, Faculty of Medicine and Health Sciences, Erasmus University, Rotterdam, The Netherlands.
Klootwijk
W
W
Linkels
E
E
Jeucken
P H
PH
Allaerts
W
W
Hofland
L J
LJ
Everts
M E
ME
Kramer
P
P
de Jong
F H
FH
van Haasteren
G A
GA
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002478:Cells, Cultured; D004971:Estrus / Q000378:metabolism; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism* / Q000502:physiology
D007987:Gonadotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; C042691:LHRH, N-acetyl-(4-chlorophenylalanyl)(1)-(4-chlorophenylalanyl)(2)-tryptophyl(3)-arginyl(6)-alanine(10)-; C059697:pyroglutamyl-glutamyl-proline amide; D011761:Pyrrolidonecarboxylic Acid