Inhibition of prolactin secretion from the male rat anterior pituitary by cryptic sequences of prothyrotropin releasing hormone, ProTRH178-199 and ProTRH186-199.
Previous studies have shown that intronic peptide sequences in the prohormone for thyrotropin-releasing hormone (TRH) have physiological actions on pituitary hormone secretion. The aim of this investigation was to examine the effect of the cryptic peptides, prothyrotropin- releasing hormone(178-199) (ProTRH(178-199)) and ProTRH(186-199), on prolactin (PRL) release from the anterior pituitary. Perifusion studies were performed with anterior pituitaries obtained from individual adult male Sprague Dawley rats at 70 90 d of age. Perifusate was collected in 5-min fractions for 25 min prior to peptide administration and for 60 min afterward. Pituitaries were perifused with a single 5 min pulse of either 2, 10, or 40 nM concentrations (peak pulse) of each peptide or the vehicle. Sixty minutes after peptide administration, a 200 mM pulse of potassium chloride was delivered to check tissue viability. Prolactin was measured in the perifusate by radioimmunoassay. Results showed that both peptides induced a significant long-term suppression of prolactin secretion that was still evident at 60 min after peptide exposure. ProTRH(186-199) was similar to ProTRH(178-199) in suppressing prolactin release at the 2 and 40 nM dose, suggesting that the amino acid sequence necessary for prolactin inhibition is contained within the smaller peptide fragment. These data indicate that a cryptic sequence within the proTRH peptide can have biological activity at the level of the anterior pituitary gland in regulating prolactin secretion.
Alexander
Thomas H
TH
Department of Psychology, San Diego State University, CA 92120, USA.
Handa
Robert J
RJ
McGivern
Robert F
RF
D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011498:Protein Precursors / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D013997:Time Factors
D010446:Peptide Fragments; D011498:Protein Precursors; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; C046418:pro-thyrotropin releasing hormone; D011761:Pyrrolidonecarboxylic Acid